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r 


THE MAKING, SHAPING 

AND 

TREATING OF STEEL 


BY 

J. M. CAMP 
AND 

C. B. FRANCIS 


SECOND EDITION 

SECOND IMPRESSION 


'I 


PUBLISHED BY 

THE CARNEGIE STEEL COMPANY 


PITTSBURGH, PA. 








130 
1 c_ i k 

' ! q 


Copyright 1920 by 
Carnegie Steel Company 
Pittsburgh, Pa. 


§)CI.A630179 



NOV -4 1921 

i 

‘ * 1 I 


'W * | 









TO 

HOMER D. WILLIAMS, 

President of the Carnegie Steel Company 

AND 

HIS ASSISTANTS 

For Their Valued Suggestions and Words of Appreciation 


THIS BOOK IS DEDICATED 



PREFACE TO SECOND EDITION 


This bok has been written especially for the nontechnical employees 
of the Cariegie Steel Company, and others, who, seeking self instruction, 
may desire to secure in the shortest time possible a general knowledge of 
the metalhrgy of iron and steel. 

The bo*k is the outcome of several years experience in attempting to 
teach the metallurgy of steel to our salesmen and other nontechnical 
employees. From the first, the method pursued in this work has been that 
of taking tie students, under proper guidance, into the mills, where they 
obtain, fir;t hand and individually, such information as they desire and 
are able tc collect, and of supplementing the knowledge gained from these 
visits withtalks and explanations delivered in a classroom where conditions 
are more fivorable for this kind or instruction than they are in the mills. 
These talk, in a condensed form, were put in writing, and a copy given 
to each of the students. As the demand for these lectures increased, it was 
decided t'iat, for the sake of convenience, they should be printed; and 
accordingly they were revised and are here assembled in the present volume. 

In order to increase the value of the book as a reference book, we 
have aimed to condense the information and to avoid every unnecessary 
word, boil by omitting all matter from the text not absolutely essential 
and by th£ free use of tables, drawings and diagrams, which we permit to 
tell their )wn story. However, knowing our readers will be men imbued 
with a desre to learn, we have not avoided discussing many scientific aspects 
) of our sibjects. But here we have tried to make it easy even for the 
general reader. We have aimed to use language as simple as possible, 
consisted with clearness, and to treat our subjects in such a way that, 
aside fron what a limited education supplies, no prerequisites will be 
required. We start with the elementary subjects of Physics and 
Chemistry, the logical prerequisites, and build our metallurgy upon that 
foundation The book will, therefore, prove of most value to those 
connectec with the steel business, and not technically educated, who are 
really amious to learn more about the wonderful industry in which they 
are engaged. For such as these, we have aimed to make this book at 
least a stepping stone to higher and better things. 




tit 


2S 


CIS 


With regard to the subject matter of the book, we claim 
the way of originality. We have.no new theories to advance 
discoveries to reveal. Our aim throughout has been to describe 
and things as they are and to explain the causes for their being 
rather than to tell how they might be or how they ought 
accomplish our first purpose, we have been compelled to rely n 
our personal observation and experiences, but in explaining th 
things we have freely consulted all those whose published opini 
to each particular subject have been available and of value 
therefore, indebted to many for aid, and to all these we wis 
our thanks. Wherever we have drawn upon these sources of 
we have aimed to give the credit to the authors by mention 
or by foot note references. As guides to collateral rea* 
references will have an additional value to our readers. We 
thank the superintendents and the many heads of departments of 
plants for the courtesies they have shown us and for the many b : 
uable information which they were ever ready to give. 


little in 
,nd no new 
conditions 
they are, 
o be. To 
ainly upon 
causes of 


alo 


relating 
We are, 
express 
^formation 
the text 
ing these 
desire to 


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>ur various 
s of val- 









TABLE OF CONTENTS 

PART I. 

MAKING OF STEEL 

Some Principles of Physics and Chemistry 

I. Introduction 

Iron, the Master Metal. 

Metallurgy defined.. 

Matter. 

a. Fundamental Laws and States of Matter.... 

b. Molecules. 

c. Sciences of Matter. 

SECTION I. Physical Properties of Matter. 

1. Classes of Properties. 

a. General Properties: 


CHAPTER 

SECTION 

1 . 

2 . 

3. 


i. Inertia. 

ii. Extension. 

iii. Mass. 

iv. Density and Specific Gravity, 

v. Porosity. 

vi. Impenetrability. 


b. Special Properties. 


SECTION II Energy, Heat and Temperature and the 

Ether: 

1. Ergy—Law of Conservation. 

Kinds of Energy—Kinetic and Potential.. 

2. Ht and Temperature. 

1 Effects of Heat—Law of gas expansion and 

kinetic theory. 

1 Temperature Scales. 

Measurement of Heat. 

3. Thither. 


1 

2 

2 

2 

2 

3 

3 

3 

3 

4 
4 
4 
4 
4 

4 


i. 

Cohesion and Adhesion. 

. 4 

ii. 

Elasticity. 

. 4 

iii. 

Plasticity. 

. 5 

iv. 

Ductility. 

. 5 

V. 

Malleability. 

. 5 

vi. 

Hardness. 

. 5 

vii. 

Crystallization. 

. 5 

viii. 

Diffusion. 

. 5 

ix. 

Effusion. 

. 5 

X. 

Absorption. 

. 5 


5 

6 
6 

6 

6 

7 

7 














































Vlll 


TABLE OF CONTENTS 




SECTION IV. Changes in Matter: 

1. Physical and Chemical Changes. 8 

2. Mechanical Mixtures and Chemical Compounds: 

a. Solutions and Alloys. 

b. Acids, bases, salts, and non-electrolytes .... 

3. The Chemical Elements. 9 

a. Classification of the elements. 9 

b. Chemical Symbols. 9 

c. Fundamental Laws of Chemical Change;.... 9 

Definite and Multiple Proportions. 9 ( 

SECTION V. The Atomic and Electron Theories: 

1. Atoms.. 10 

a. Atomic weights. 10 

b. Valence. 10 

c. Table of Elements with symbols, etc. 11 

2. Electrons. 13 

SECTION VI. Chemical Formula and Reactions: 

1. Formula of Compounds. 13 

2. Formula of Molecules of Elements. 13 

3. Chemical Equations. 13 

a. Balancing reactions. 14 

b. Radicals. 14 

4. Ions and Electrolysis. 14 

5. Dry and Wet Chemistry. 15 

a. Acids, bases and salts of Dry Cheistry.. 15 

b. Table of anhydrides. 16 

6. Kinds of Reactions. 16 

7. Laws of Chemical Reactions.. 17 

SECTION VII. Chemical Nomenclature: 

1. The General Principle of Nomenclature. 18 

2. Terminology of Binary Compounds. 18 

3. Terminology of Ternary Compounds. 18 

4. Terminology of Acids. 18 

5. Terminology of Bases. 19 

6. Terminology of Salts. 19 

SECTION VIII. Chemical Calculations: 

1. Kinds of Problems. 19 

2. Problems involving weight only. 19 

3. Problems involving volume only. 20 

4. Problems involving weight and volume. 21 


00 oo 










































TABLE OF CONTENTS ix 


SECTION IX. Description of Elements Important in 

Iron and Steel Making: 

1. Occurrence, Preparation, Properties and Some 

Compounds of Oxygen. 22 

2. Occurrence, Preparation, Properties and Some 

Compounds of Hydrogen. 22 

3. Occurrence, Preparation, Properties and Some 

Compounds of Sulphur. 23 

4. Occurrence, Preparation, Properties ' and Some 

Compounds of Carbon. 23 

5. Occurrence, Preparation, Properties and Some 

Compounds of Silicon. 24 

6. Occurrence, Preparation, Properties and Some 

Compounds of Nitrogen. 25 

7. Occurrence, Preparation, Properties and Some 

Compounds of Phosphorous. 25 

8. Occurrence, Preparation, Properties and Some 

Compounds of Calcium and Magnesium. 25 

9. Occurrence, Preparation, Properties and Some 

Compounds of Aluminum. 26 

10. Occurrence, Preparation, Properties and Some 

Compounds of Chromium. 26 

11. Occurrence, Preparation, Properties and Some 

Compounds of Manganese. 27 

12. Occurrence, Preparation, Properties and Some 

Compounds of Iron. 27 

CHAPTER II. Refractories. 

SECTION I. Nature of Refractories: 

1. Importance. 28 

2. Requirements of Refractories. 28 

3. Classes of Refractories....:. 28 

SECTION II. Acid Refractories: 

1. Chemical Composition. 29 

2. Silica Bricks. 29 

3. Clay. 29 

a. The Impurities in Clays. 29 

b. The Process of Making Fire Clay Brick- 30 


























TABLE OF CONTENTS 


SECTION III. Basic Refractories: 

1. Magnesia. 30 

2 . Lime. 30 

3. Dolomite. 31 

4. Bauxite. 31 

SECTION IV. Neutral Refractories: 

1. The Ideal Furnace Lining. 31 

2 . Graphite. 31 

3. Chromite.. 31 

4. Protection for Refractories. 31 

5. Table—Chemical Analyses of Refractories. 32 

SECTION V. Testing Refractories: 

1. Trial Tests and Laboratory Tests. 33 

2. Fusion Temperature. 33 

3. Resistance to Compression. 33 

4. Expansion and Contraction. 34 

5. Slagging Test. 34 

6 . Density. 34 

7. The Impact Test. 35 

8 . The Abrasion Test. 35 

9. Spalling Test. 35 

CHAPTER III. Iron Ores. 

SECTION I. Ores and the Iron Bearing Minerals: 

1. Minerals and Ores. 36 

2. The Iron Bearing Minerals. 36 

a. Magnetite Group. 37 

b. Hematite Group. 37 

c. Limonite or Brown Ore Group. 37 

d. The Carbonate Group. 37 

3. The Mineralogical Make-up of Iron Ores. 37 

SECTION II. Valuation of Ores: 

1 . Factors in the Valuation of Ores. 38 

a. The Impurities that Are Never Reduced in 

the Blast Furnace. 39 

b. The Impurities that May Be Partially 

Reduced. 39 

c. The Impurities Always Reduced. 40 

d. Water. 40 

e. Accessibility.. 41 




































TABLE OF CONTENTS xi 


SECTION III. The Birmingham District: 

1. Location and General Geology. 42 

2. Method of Mining. 42 

SECTION IV. The Lake Superior District: 

1. Importance, Location and General Geology.. 42 

a. The Marquette Range. 43 

b. The Menominee Range. 43 

c. The Gogebic Range. 43 

d. The Vermilion Range. 46 

c. The Missabe Range. 46 

f. The Cuyuna Range. 47 

SECTION V. Mining The Lake Ores: 

1. Prospecting and Exploration. 47 

a. Prospecting. 47 

b. Drill Exploration. 47 

2. Methods of Mining. 50 

a. Open Pit Mining. 50 

i. Steamshovel Mining. 50 

ii. Milling. 52 

iii. Scramming. 53 

iv. Advantages of Open Pit Mining. 53 

b. Underground Mining—Slicing. 53 

i. Advantages of the Slicing System of 

Mining. 55 

ii. Depth of Mine Shafts.... 55 

3. Grading the Ores. 55 

4. Transporting the Ores. 56 

5. Mining and Grading in Winter. 57 

CHAPTER IV. Fuels. 

SECTION I. Some Pre-Requisites to the Study of Fuels: 

1. Introductory. 58 

2. Sensible and Specific Heat. 58 

3. Latent Heat and Change of State. 59 

a. Laws of Fusion. 59 

b. Laws of Evaporation. 59 

c. Laws of Ebullition. 59 

4. Transmission of Heat.'. 59 

5. Fuels and Combustion. 60 

6. Fuels and Chemical Energy. 60 

7. Measurement of Calorific Power. 60 

8. The Calorific Power of Some Common Elements.. 61 

9. Calculating Calorific Power. 61 

10. Practical Heat Tests. 62 








































Xll 


TABLE OF CONTENTS 


SECTION I.—Continued. 

11. Laboratory Heat Tests. 62 

12. Calorific Intensity. 63 

13. Methods of Conserving Heat. 63 

14. Pyrometers. 64 

a. Specific Heat, or Water, Pyrometer. 64 

b. Electric Resistance Pyrometers. 64 

c. Thermo-Electric Pyrometers. 64 

d. Radiation Pyrometers-!. 65 

e. Optical Pyrometers. 65 

SECTION II. Classification of Fuels: 

1. Table—Classification of Fuels. 66 

2. Plan of Study. 67 

SECTION III. Incidental and Liquid Fuels: 

1. Incidental Fuels. 67 

2. Tar. 67 

3. Petroleum.-. 68 

a. Composition of Petroleum. 63 

b. Hydrocarbons—Generalized, Empirical and 

Structural Formulas. 6S 

c. Table—The Different Homologous Series of 

Hydrocarbons. 69 

d. Fuel Oil and Other Products of Petroleum. 69 

SECTION IV. Gaseous Fuels: 

1. Advantages of Gaseous Fuels. 70 

2. Table—Hydrocarbons in Natural Gas and Petroleum 70 

3. Natural Gas. 71 

4. Artificial Gases. 71 

a. Table—Composition of Gaseous Fuels. 71 

b. Principle of the Gas Producer. 71 

c. Factors Affecting the Efficiency of the Producer 73 

d. The Hughes Producer as an Example of 

Mechanically Poked Producer. 73 

e. Conditions and Reactions. 74 

f. Operation of the Hughes Producer. 75 

SECTION V. The Solid'Natural Fuels: 

1. Analysis of Solid Natural Fuels:. 75 

a. Table—Analysis of a Solid Fuel, Coal, by 

the Three Different Methods. 76 

2. Wood. 76 

3. Peat. 77 

4. Lignite and Brown Coal. 77 














































TABLE OF CONTENTS xiii 


SECTION V.—Continued. 

5. Table—Approximate Analyses of the Different 

Solid Fuels. 78 

6. Diagram—Depicting Geologic Periods in which 

Gas, Oil, and the Valuable Minerals are Found. . 79 

7. Coal. 80 

a. Bituminous Coal. 80 

b. Ash in Coal. 80 

SECTION VI. Prepared Solid Fuels: 

1. Powdered Coal. 81 

a. Requirements for Use of Powdered Coal. 81 

b. Advantages of Powdered Coal. 82 

c. The Sharon Powdered Coal Plant. 82 

i. Description of Pulverizing Plant. 82 

d. Clairton and Homestead Powdered Coal Plants 83 

2. Coke. 85 

a. Methods of Manufacturing Coke. 85 

SECTION VII. The Beehive Process for the Manufacture 

of Coke: 

1. The Continental No. 1 Plant of the H. C. Frick 

Coke Company. 86 

a. The Mine. 86 

b. The Coking Plant. 86 

i. Construction and Arrangement of Ovens 86 

ii. Waste Heat System. 87 

iii. Charging the Ovens. 87 

iv. The Coking Process. 88 

v. Watering and Drawing the Coke. 89 

vi. Longitudinal Ovens. 90 

SECTION VIII. The By-Product Process for Manufac¬ 
turing Coke: 

1. General Features of the Process.•. 90 

2. Advantages of the By-Product Process. 91 

3. The Plant of the Clairton By-Product Coke 

Company. 91 

a. Construction of the Ovens. 93 

b. Heating the Ovens. 95 

c. Drying and Heating New Ovens. 96 

d. Operation of the Ovens. 96 





























XIV 


TABLE OF CONTENTS 


SECTION IX. The By-Product Plant: 

1. The Volatile Matter of Coal. 98 

2. Gas Mains and Coolers. 98 

3. Separation of the Tar and Ammonia Liquor.... 99 

4. Compressors and Tar Extractors. 99 

5. Recovery of Ammonia. 100 

6. Debenzolating the Gas. 101 

SECTION X. The Benzol Plant: 

1. Light Oil. 101 

2. Composition of Light Oil. 102 

3. Construction and Principles of the Still. 102 

4. Operation of the Crude Still. 102 

5. Washing the Products of the Crude Stills. 103 

6. The Pure Stills. 103 

SECTION XI. Some Properties and Uses of the Raw By- 

Products from the Coke Works: 

1. Characteristics of Benzol, Toluol and Naphtha. 105 

a. Some Members of the Benzene Series, and 

their Physical Properties. 106 

2. Commercial Benzol. 107 

a. Uses of Commercial Benzol. 107 

b. Motor Benzol. 107 

3. Properties and Uses of Pure Benzol, or Benzene. ... 109 

a. Table—Diagram Showing Some of the 

Products Derived from Benzene, Their 
Formulas and Their Uses. 108 

b. Table—Reactions Showing How Phenol, 

Picric Acid and Resorcinol may be 
Derived from Benzene. 110 

c. Table—Reactions Showing How Aniline and 

Benzidine are Derived from Benzene. 109 

4. Uses of Toluene. Ill 

a. Table—Some Products Derived from Toluene, 

Their Formulas and Uses. 112 

b. Commercial Toluol and Solvent Naptha. Ill 

5. Uses of Naphthalene. 113 

a. Table—Showing Some Products Derived 

from Naphthalene. 114 

6. Tar. 114 

a. Diagram—Illustrative of the Refining of Tar. 115 

7. Ammonia. 116 

a. Ammonium Sulphate. 116 

b. Use of Ammonium Sulphate as a Fertilizer.. 116 





























TABLE OF CONTENTS 


xv 


CHAPTER V. Fluxes and Slags. 

SECTION I. Fluxes: 

1. Smelting and the Functions of a Flux. 117 

2. The Selection of the Proper Flux for a Given Process 117 

3. Acid Fluxes. 118 

a. Alumina. $... 118 

4. Basic Fluxes. 118 

a. Available Base. 118 

b. Limestone. 119 

c. Supply of Limestone. J19 

d. Action of Limestone in Furnaces. 119 

5. Neutral Fluxes. 120 

SECTION II. Slags: 

1. Slag. 120 

2. Functions of Slags. 120 

3. Importance of Slags. 120 

4. Chemical Composition of Slags. 121 

5. Relation of Acids to Bases in Blast Furnace Slags.. 121 

6. Ratio of Acids to Bases in Open Hearth Slags122 

7. Acid to Base in Acid Furnaces. 122 

8. Electric Steel Furnace Slags. 122 

9. Acids Formed by Silicon. 122 

10. So-called Acid and Basic Slags. 123 

11. Classification of Slags. 123 

12. Uses of Slags. 124 

CHAPTER VI. The Manufacture of Pig Iron. 

SECTION I. Some Interesting Historical Facts: 

1. Early History of Iron. 125 

2. Old American Furnaces. 126 

3. The Importance of Iron. 126 

SECTION II. Composition and Constitution of Pig Iron: 

1. Constitution of Pig Iron. 126 

2. Chemical Elements in Pig Iron. 127 

a. Carbon. 127 

b. Silicon. 127 

c. Manganese. 128 

d. Sulphur. 128 

e. Phosphorus. 129 

3. Grading Pig Iron. 129 



































XVI 


TABLE OF CONTENTS 


SECTION III. A Brief Outline of the Process and Equip¬ 
ment for the Manufacture of Pig Iron: 

1. Trend of Modern Improvements. 130 

2. Essentials of the Process. 130 

3. Essential Equipment. 130 

SECTION IY. Construction of the Blast Furnace Proper: 

1. The Gross Features of the Furnace Proper .. 131 

2. The Foundation. 131 

3. The Hearth or Crucible.. 132 

4. The Bottom. 132 

5. Tapping Hole.. 132 

6. Cinder Notches.. 134 

7. Tuyeres. 134 

8. Tuyere Connections. 134 

9. Boshes. 135 

10. Mantle. 136 

11. Shaft, or Stack, and In-Walls. 136 

a. Thick Wall Type. 136 

i. The Furnace Lines and Bosh Angles. 136 

b. Intermediate, or Semi-Thin, Wall Type. 137 

c. Thin Walled Type.'... 137 

d. Furnace Linings. 137 

12. Water Trough. 139 

13. Tops.;.. 139 

a. Stock Distributor. 140 

b. Hoisting Appliances. 140 

c. Top Openings. 140 

d. General Consideration for Top Construction.. 141 

14. Runners. 141 

SECTION V. Blast Furnace Accessories: 

1. The Stoves. 142 

a. Stove Burners and Valves. 143 

, b. Other Stove Openings. 143 

c. Stove Linings. 145 

2. Dust Catcher and Gas Mains. 146 

3. Arrangement of Furnaces and Cleaning Plant at 

Duquesne. 146 

a. Primary Division. 148 

i. Methods of Scrubbing the Gas. 148 

ii. The Fans. 149 

iii. Water Separator. 149 

b. The Secondary Division. 149 

SECTION VI. Equipment for Handling Raw and Finished 

Material- 

1. The Boiler House, Power Plant, Pumping Station, 

Blowing Engines, etc. 150 















































'TABLE OF CONTENTS xvii 


SECTION VI.—Continued. 

2. Dry Blast. 150 

3. Cold and Hot Blast Mains. 150 

4. Appliances for Handling Ores, Coke and Stone. 150 

5. Stock House Equipment. 151 

6. Disposal Equipment for the Iron. 152 

7. Equipment for Slag Disposal. 152 

SECTION VII. Operating the Furnace: 

1. Blowing In. 152 

2. Drying. 152 

3. Filling. 153 

4. Lighting. 153 

5. Heating the Bottom. 154 

6. The Heating of the Stoves. 154 

7. Tapping. 154 

8. Care of Runners. 155 

9. Sampling the Iron. 155 

10. Tapping Slag. 156 

11. Changing Stoves. 156 

12. Charging the Furnace. 156 

13. Some Irregularities of Furnace Operation. 157 

a. Slips. 157 

b. Scaffolding. 158 

c. Chimneying and Hot Spots. 158 

d. Loss of Tuyeres and Chilled Hearth. 158 

14. Uncertainties and Variables in Furnace Control_ 158 

15. Banking. 159 

16. Blowing Out. 159 

SECTION VIII. The Blast Furnace Burden: 

1. Burdening the Furnace. 159 

a. Outline of a Method for Solving a Burdening 

Problem. 161 

b. The Burden Sheet. 161 

2. Table 27. Analysis of Raw Materials Used in the 

Blast Furnace.i. 160 

SECTION IX. Chemistry of the Process: 

1. Methods of Investigating the Reactions of the Blast 

Furnace. 163 

2. The Functions of Oxygen and Carbon. 163 

3. Behavior of Nitrogen in the Furnace. 165 

4. Action of Phosphorus in the Furnace. 165 

5. Disposition of Sulphur in the Furnace. 165 

6. Behavior of Silicon. 165 

7. Action of Calcium and Magnesium. 166 

8. Action of Aluminum. 166 










































XV111 


TABLE OF CONTENTS 


SECTION IX.—Continued. 

9. Action of Less Abundant Elements. 166 

10. The Reactions Within the Furnace. 167 

11. Tracing the Materials Through the Furnace. 170 

12. Conditions Affecting the Amount of Silicon and 

Sulphur in the Metal. 171 

CHAPTER VII. The Bessemer Process of Manufacturing Steel. 

SECTION I. The Classification of Ferrous Products: 

1. Introductory. 172 

2. Pig Iron and Cast Iron. 172 

3. Malleable Cast Iron. 172 

4. Wrought Iron. 173 

5. Steel. 173 

6. Methods of Making Steel. 174 

7. General Principles of the Methods of Purifying 

Pig Iron. . 175 

SECTION II. Principles and History of the Bessemer 

Process: 

1. Principles of the Process. 175 

2. Some Incidents Connected with the Early History 

of the Process. '.... 176 

3. Importance of Manganese. 176 

4. Thomas and Gilchrist Process. 177 

5. Other Improvements. 177 

6. Plan of Study. 177 

SECTION III. Equipment and Arrangement of the Edgar 

Thomson Plant: 

1. The Converter House. 177 

2. The Larger Accessories. 179 

a. The Cupolas. 179 

b. Charging the Cupola. 180 

c. The Blast. 180 

d. The Mixers. 181 

i. Importance of the Mixer.. . 181 

e. The Stripper. 181 

f. The Casting Equipment. 182 

i. The Ingot Moulds. 182 

SECTION IV. Converter Construction and Repairs: 

1. General Features Pertaining to Converters. 183 

2. Parts of Converter.•. 183 

a. Lining of the Converter. 184 

b. The Bottom. 185 

i. Relining the Bottom. 185 




































TABLE OF CONTENTS xix 


SECTION V. The Converter in Operation — Purifying 

the Metal: 

1. Charging the Vessel. 187 

2. The Blow. 187 

3. Controlling the Blow. 188 

4. The End of the Blow. 189 

SECTION VI. Finishing Operations — Converting the 

Purified Metal Into Steel: 

1. Deoxidation and Recarburization. 190 

2. Loss of Recarburizer and Deoxidizer. 191 

3. Examples of Recarburizing. 191 

4. Ladle Reaction. 191 

5. Teeming. 192 

6. Sampling the Steel for Chemical Analyses. 192 

SECTION VII. Chemistry of the Process: 

1. The Order of Elimination of the Elements. 193 

2. The Laws and Conditions Governing the Reactions 

in the Converter. 193 

3. Reactions of the First Period. 194 

4. Reactions of the Second Period. 195 

5. Chemistry of Recarburizing and Deoxidizing. 196 

CHAPTER VIII. The Basic Open Hearth Process. 

SECTION I. Some General Features of the Siemens 

Process: 

1. Early History of the Process. 198 

2. Principles of Siemens Pig and Ore Process.... 199 

3. Advantages of the Process. 199 

4. Mechanical Changes and Improvements in Siemen’s 

Process. 200 

5. Metallurgical Improvements. 200 

6. The Process for the Pittsburgh District. 201 

SECTION II. Equipment for a Modern Basic Open 

Hearth Plant: 

1. The Modem Plant. 202 

2. Calcining Plant. 202 

3. Fuels. 203 

4. Fuel Consumption. 203 

5. Hot Metal Mixer. 204 

6. Spiegel Cupolas. 204 

7. The Steel Ladles. 204 

8. The Stripper. 205 

9. Moulds. 205 

10. The Charging Machine..,. 206 

11. Charging Boxes. 20 < 

12. Stock Yard. 207 

13. Arrangement of the Plant. 207 







































XX 


TABLE OF CONTENTS 


SECTION III. Chief Features of Basic Open Hearth 

Construction: 

1. Parts of the Open Hearth Furnace and Their 

Arrangement. 209 

2. The Furnace Proper. 209 

a. The Hearth. 210 

b. The Walls. 210 

c. The Roof. 211 

d. The Bulk Heads. 211 

3. The Ports. 211 

4. The Up-and-Down-Takes. 211 

a. Arrangement of Up-and-Down Takes for 
Natural Gas, Coke Oven Gas, Powdered 
Coal and Tar. 212 

5. Slag Pockets. 212 

6. Regenerators for Producer Gas. 212 

7. Regenerators for Natural and Coke Oven Gases.... 216 

8. Regenerators for Powdered Coal. 217 

9. Flues and Valves. 217 

10. The Stack. 217 

SECTION IV. Operation of a Basic Open Hearth— 

Purifying the Metal: 

1. Furnace Attendants and Their Duties. 218 

2. Preparation of the Furnace for its First Charge.... 218 

3. Charging. 219 

a. The Order of Charging Raw Materials. 220 

4. Melting Down the Charge. 220 

5. The Addition of the Hot Metal. 221 

6. The Purification Periods. 221 

a. The Ore Boil. 222 

i. The Run off. 222 

b. The Lime Boil. 223 

c. The Working Period. 223 

i. Methods of Working the Heat. 223 

ii. Testing for Carbon. 224 

iii. Control of Carbon and Temperature ... 224 

iv. Judging the Temperature of the Bath... 225 

7. Tapping. 225 

SECTION V. Finishing the Heat—Making Steel from 

the Purified Metal: 

1. Methods of Finishing the Steel. 226 

2. Some Features that Make the Finishing of the Steel 

Difficult. 227 

3. Teeming. 228 

4. Sampling. 229 



































# 

TABLE OF CONTENTS X xi 


SECTION VI. Keeping the Furnace in Repair: 

1. Preparation of the Furnace for the Next Charge. 229 

2. Furnace Troubles. 230 

3. Repair Materials. 231 

a. Dolomite. 231 

b. Magnesite. 231 

c. Chrome Ore. 231 

SECTION VII. Chemistry of the Basic Process: 

1. Some of the Principles and Conditions Involved.,. 232 

2. Properties of Iron and Its Oxides. 232 

a. The Importance of Ferrous Oxide, FeO, in the 
Part Played by the Oxides of Iron in the 
Process. 233 

3. Properties of Silicon and Its Oxide, Silica. 234 

4. Properties of Manganese and Its Oxides. 235 

5. Sulphur and Its Oxides. 236 

a. Sulphur from the Fuel. 237 

6. Phosphorus and Its Oxides. 237 

7. Carbon and Its Oxides. 238 

a. The Action of the Limestone. 239 

b. Effect of Carbon Elimination on Slag 

Composition. 239 

8. The Order of Elimination. 239 

a. Factors Opposing this Order of Elimination 240 

9. Resume. 241 

CHAPTER IX. Manufacture of Steel in Electric Furnaces. 

SECTION I. Introductory: 

1. The Plan of Study. 243 

2. Force, Work, Energy and Potential. 243 

3. Power. 240 

4. Transmission of Energy. 244 

5. Electromotive Force (E. M. F.). 246 

SECTION II. The Development of Electromotive Forces 

—or “Generation of Current:” 

1. Methods for Setting Up Electric Currents. 246 

2. Magnetism..,. 246 

a. Magnets and Magnetic Substances. 247 

b. Magnetic Fields and Electric Currents. 248 

3. Electromagnetic Induction. 249 

a. Laws of Electromagnetic Induction. 250 

b. The Dynamo. 250 

SECTION III. Kinds of Current: 

1. Alternating Current. 251 

a. Graphic Representation of Alternating Current 252 




































XXII 


TABLE OF CONTENTS 


SECTION III.—Continued. 

2. Direct Currents. 253 

3. Polyphase Currents. 253 

4. The Two Schemes of Wiring for Three Phase Current 254 

SECTION IV. Transmission of the Current: 

1. Ohm’s Law. 256 

2. Resistance of Conductors. 256 

a. Effect of Temperature on Conductors. 257 

b. Resistance in Series and Parallel. 258 

c. Currents Through Divided Circuits. 259 

3. Self-induction, Impedance, Power Factor. 259 

4. Heat Developed in Conductors. 259 

5. The Stationary Transformer,. 260 

a. Kinds of Stationary Transformers. 260 

SECTION V. The Utilization of the Current in Electric 

Furnaces: 

1. Effects Produced by Electric Current. . 261 

a. Chemical Action Produced by the Electric 

Current. 261 

i. Electrical Units of Measurements. 262 

b. The Magnetic Influence of the Current_ 262 

2. Heating the Bath. 262 

a. Heating by Direct Resistance. 263 

b. Indirect Resistance Heating. 264 

c. Arc Heating... 264 

d. Methods of Applying the Arc in Arc Furnaces. 265 

i. The Stassano Furnace. 265 

ii. Girod Furnaces. 266 

iii. The Principle of the Heroult Furnace.. 266 

3. Some General Conclusions. 267 

SECTION VI. General Features Pertaining to the 

Metallurgy of Steel Made by Electro- 
Thermal Processes: 

1. Advantages of Electric Heating. 267 

2. Refining Procedure. 267 

a. The Oxidizing Period. .*.. 268 

b. The Reducing Period. 269 

i. Oxygen. 269 

ii. Removal of Sulphur. 269 

c. The Finishing Period. 270 

3. Some Comparisons. 271 

4. Fluxing Materials. 271 

5. General Manufacturing Practice. 271 





































TABLE OF CONTENTS xxiii 


SECTION VII. The Duquesne Plant — Features Pertain¬ 
ing to its Construction: 

1. Equipment. 275 

2. Construction of the Furnace Shell. 275 

3. The Furnace Lining. 275 

4. The Roof. 277 

5. Controlling the Electrodes. 277 

a. The Electrode Holders. 277 

6. The Electrodes. 279 

7. Furnace Openings. 279 

SECTION VIII. Operation of the Furnace: 

1. Practice at Duquesne Plant. 279 

a. Charging. 280 

b. Deoxidizing. 280 

c. Finishing the Heats. 281 

d. Tapping and Teeming. 281 

e. Scrap Heats. 281 

SECTION IX. The Chemistry of the Process: 

1. Deoxidation of the Bath. 286 

2. Desulphurizing the Metal. 286 

3. Difficult Specifications. 288 

SECTION X. Properties and Uses of Electric Steel: 

1. Properties of Electric Steel. 289 

2. Illinois Steel Company’s Tests on Rails. 290 

3. Uses of Electric Steel. 291 

4. Summary. 291 

CHAPTER X. The Duplex and Triplex Processes. 

SECTION I. General Features of the Duplex Process: 

1. What the Duplex Process Is. 293 

2. Advantages and Disadvantages of the Process.... 293 

3. Methods of Duplexing. 294 

4. The Talbot Furnace. 294 

SECTION II. Operation of the Process: 

1. An Example of the Duplexing Process..'. 295 

2. Preparing the Furnace for Charging. 295 

3. Charging Molten Metal from the Converters for 

the First Heat. 295 

4. Tapping and Recarburizing the First Heat. 296 

5. Preparing the Furnace for the Second Heat. 296 

6. Closing Down the Furnace for the Week End. 297 

7. Slag. 297 

SECTION III. Combination Processes in the South: 

1. The Duplex Process in the South. 297 

2. The Southern Triplexing Process. 298 








































XXIV 


TABLE OF CONTENTS 


PART II. 

THE SHAPING OF STEEL 

CHAPTER I. The Mechanical Properties of Steel. 

« 

SECTION I. General Remarks Pertaining to the Testing 

of Steel: 

1. The Factors that Affect the Mechanical Properties 

of Steel. 299 

2. The Two Objects in the Testing of Steel. 299 

3. Relative Importance of Physical and Chemical Testing 300 

4. Nature of Physical Testing. 300 

SECTION II. The Testing of Structural and Other Soft 

Steels: 

1. The Pulling Test. 301 

a. Procuring the Test Pieces. 301 

b. Preparation of the Test Piece. 302 

c. Pulling the Test. 303 

i. Graphic Representation of Tests. 304 

ii. Reasons for the Points of Yield and 

Maximum Stress. 304 

d. Examination of Test After Pulling... 305 

e. Calculating the Results of the Test. 306 

2. The Modulus of Elasticity, or Young’s Modulus.. . 307 

3. Relative Importance of the Mechanical Properties as 

Determined by the Pulling Test.307 

4. Bending Tests. 308 

SECTION III. The Testing of the Higher Carbon and 

Heat Treated Steels: 

1. Kinds of Tests Applied to the Higher Carbon and 

Heat-treated Steels. 308 

2. The Tensile Test. 308 

3. The Impact Test. 309 

4. Hardness Tests..... 309 

a. Shore Scleroscope. 310 

b. Brinell Hardness. 310 

i. Relation of Brinell Number to Tensile 

Strength. 311 

CHAPTER II. The Mechanical Treatment of Steel. 

SECTION I. Methods and Effects of Mechanically 

Working Steel: 

1. Methods of Shaping Steel.•. 312 

2. Benefits of Mechanical Working... 312 

3. Hot and Cold Working. 313 































TABLE OF CONTENTS 


XXV 


SECTION II. Summary of the History and Principles of 

Working Steel: 

1. The Three Methods for Mechanically Working Steel. 316 

a. Hammer Forging. 316 

i. Principles and Effects of Hammering.... 317 

b. The Forging Press. 317 

i. The Effect of Pressing. 317 

ii. Advantages of the Press. 318 

c. Rolling. 318 

i. Principle and Effect of Rolling. 319 

ii. Rolling Compared with Hammering and 

Pressing. 320 

iii. Rolling and Pressing Ingots. 321 

CHAPTER III. Essentials of Rolling Mill Construction and 

Operation. 

SECTION I. The Rolls—Their Preparation and Arrange¬ 

ment: 

1. Parts and Equipment of the Simplest Type of 

Rolling Mill. 322 

2. The Rolls and Their Parts. 322 

a. The Manufacture of Rolls. 323 

b. The Sand Roll. 323 

i. The Materials Used in Sand Cast Rolls.. 324 

c. Chilled Rolls. 324 

i. Difficulties in Making Chilled Rolls. 326 

d. Steel Rolls. 326 

e. Other Rolls. 327 

f. The Size of Rolls. 327 

g. Roll Design. 327 

i. Methods of Procedure in Designing Rolls 328 

ii. Difficulties in Designing Rolls. 328 

h. Turning the Rolls. 329 

i. Dressing the Rolls. 329 

3. Types of Mills. 330 

SECTION II. Parts of the Mill Essential to the Oper¬ 
ation of the Rolls: 

1. The Chocks. 331 

a. The Arrangement of the Chocks. 331 

b. The Function of the Chocks. 332 

2. The Housings. 332 

a. The Adjusting Equipment. 333 

































XXVI 


TABLE OF CONTENTS 


SECTION II.-Continued. 

3. The Pinions. 333 

4. The Connections. 334 

5. Guides and Guards. 334 

6. Additional Equipment. 335 

SECTION III. Some General Features Pertaining to 

Operation of the Rolling Mill: 

1. The Mill Force. 336 

a. Duties of the Roller. 336 

2. Fins. 336 

3. The Different Passes and Stands. 337 

4. Factors Affecting the Rolling Operation. 337 

5. Effects of Temperature. 337 

6. Effect of Chemical Composition. 338 

7. The Effect of Speed. 339 

8. Draught. 339 

9. The Effect of Diameter of Rolls. 340 

CHAPTER IV. Preparation of the Steel for Rolling. 

SECTION I. Ingots and Their Defects: 

1. Preparation of Ingots. 342 

2. Ingot Defects. 342 

3. The Nature of the Cooling of an Ingot. 343 

a. Pipes. 343 

i. Methods of Reducing Waste due to.... 

the Pipe. 346 

b. Blow Holes. 346 

c. Crystallization. 348 

d. Segregation. 348 

e. Checking and Scabs. 349 

f. Slag Inclusions. 349 

4. Size and Shape of Ingots. 352 

SECTION II. The Construction of the Soaking Pit: 

1. General Features of the Pit. 352 

2. Arrangement of the Pits. 353 

3. Equipment for Handling Ingots. 353 

4. Construction of the Pits. 353 

a. The Air Regenerators. 355 

b. The Pit Covers. 356 

c. Fuel and Air Valves, etc. 357 

d. Stack-Flues and Stack. 357 

e. The Course of the Gases Through the Pits_ 358 

5. Eight Ingot Pits. 358 

6. Making up the Bottom of the Pit. 358 






































TABLE OF CONTENTS xxvii 


SECTION III. Soaking the Ingots for Rolling: 

1. Charging the Ingots. 359 

2 . Heating the Ingots .. 360 

a. Week-end Charges. 360 

b. Soaking Hot and Cold Ingots. 360 

c. Soaking Hot Spring Steel.,.. 361 

d. Soaking Low Carbon Hot Steel. 361 

e. Soaking Medium Steels. 361 

f. Soaking Screw Stock. 361 

g. Soaking Alloy Steels. 362 

3. Drawing the Ingots. 362 

4. Heat Balance of Pits. 362 

5. Disposition of Ingot Products. 363 

CHAPTER V. The Rolling of Blooms and Slabs. 

SECTION I. Introductory: 

1. Outline of the Plan of Study. 364 

2 . Blooms, Slabs and Billets. 365 

SECTION II. Some General Features Pertaining to 

Blooming Mills: 

1. Size of Blooming Mills. 366 

2. Types of Bloomers, Their Advantages and Dis¬ 

advantages. 366 

3. Drive for Reversing Mills. 368 

SECTION III. An Example of Reversing Mills—The 40" 

Mill at Duquesne: 

1. The Engine. 368 

2. Driving Connections. 368 

3. Pinions and Pinion Housings.'. 369 

4. Spindles and Coupling Boxes. 369 

5. Roll Housings. 370 

6 . Rolls. 371 1 

7. Roll Bearings. 371 

8 . Hydraulic Shears. 372 

9. Steam Shears. 372 

10. Manipulator. 373 

11 . Design of the Rolls. 373 

12. Operation of Rolling. 375 

SECTION IV. Example of a Three-high Blooming Mill: 

1. Plan of Study. 377 

2. The 40" Three-high Mill at Edgar Thomson. 377 

a. The Engine and Connections. 378 




































XXVI11 


TABLE OF CONTENTS 


SECTION IV—Continued. 

b. The Pinions and Spindles. 378 

c. The Roll Housings. 378 

d. The Rolls. 378 

e. Lifting Tables. 380 

3. Roll Design for Three-high Bloomers. 381 

a. An Example of Roll Design for Three-high 

Blooming Mill. 381 

SECTION V. The Rolling of Slabs: 

1. The Rolling of the Slab. 385 

2. The 32" Mill at Homestead as an Example of a 

Slabbing Mill. 385 

a. The Horizontal Mill. 385 

b. The Vertical Mill. 386 

3. Precautions to be Observed in Rolling Slabs. 387 

4. Removal of Scale. 388 

5. Shearing Slabs at 32" Mill. 389 

CHAPTER VI. The Rolling of Billets and Other Semi= 

Finished Products. 

SECTION I. The Three-High Billet Mill: 

1. General Features of Rolling Billets. 391 

2. Example of Three-High Billet Mill—The 28" Mill 

at Duquesne. 391 

a. Engine. 391 

b. Drive. 392 

c. Pinions and Their Housings. 392 

d. Housings and Roll Bearings. 393 

e. Rolls. 393 

f. Guide Cages. 395 

g. Tables.*.. 395 

SECTION II. The Continuous Billet Mill: 

1. General Features of the Continuous Mill. 397 

2. Advantages and Disadvantages of Continuous Mills.. 397 

3. Example of Continuous Billet Mill. 398 

a. Drive. 398 

b. Pinions and Housings. 399 

c. Rolls and Housings.. 399 

i. Adjustment of Rolls. 399 

d. Arrangement of Roll Stands and Guides. 400 

e. The Rolls. 400 

f. Cropping Shears. ;.... 401 

g. Flying Shears. 404 

h. Hot Beds. 404 






































TABLE OF CONTENTS xxix 


SECTION III. Rolling of Sheet Bars and Skelp: 

1. Difficulties and Methods of Rolling Semi-Finished Flats 406 

2. The Tongue and Groove Pass. 406 

3. Sheet Bar. 408 

4. The 21" Mill at Duquesne. 408 

a. The Layout for the Mill. 409 

b. Arrangement of the Roll Tables. 409 

c. Hot Saws and Shears. 410 

d. Drive. 410 

e. Pinions and Housings. 411 

f. Rolls and Roll Housings. 412 

SECTION IV. Some General Precautions to be Observed 

in Rolling Semi-Finished Products: 

1. Reasons for Studying Defects. 413 

2. Rough Surface Due to Scale. 413 

3. Cobbling. 414 ' 

4. Laps. 414 

5. Collar Marks. 414 

6. Guide Marks. 415 

7. Ragging Marks. 415 

8. Off Size. 415 

9. Unequal Draughts. 415 

10. Seams. 415 

11. Slivers. 415 

12. Scabs. 415 

13. Shearing Defects. 415 

14. Splits or Cracks in Billets and Blooms. 417 

15. Inspection. 417 

CHAPTER VII. The Rolling of the Heavier Finished Products 

—Plates. 

SECTION I. Preparation of the Steel for Rolling 

Finished Products: 

1. Reheating. 418 

2. Types of Reheating Furnaces. 419 

a. The Regenerative Reheating Furnace. 419 

b. The Recuperative, or “Continuous" Furnace... 421 

3. The Advantages of Continuous Reheating Furnaces... 421 

SECTION II. The Rolling of Sheared Plates: 

1. Methods of Rolling Plates. 423 

2. The 140" Mill at Homestead as an Example of a 

Sheared Plate Mill. 423 

a. The Drive and Connections. 424 


































XXX 


TABLE OF CONTENTS 


SECTION II.—Continued. 

3. Difficulties in Rolling Sheared Plates. 425 

4. The Rolling Process. 426 

5. Cooling and Straightening. 427 

6. Laying-out and Stamping. 427 

7. Test Pieces. 429 

8. Shearing. 429 

a. Shearing Tolerances. 430 

9. Size Inspection. 430 

10. Weighers. 430 

11. Checkers. 430 

12. Slip Maker. 431 

13. Recorder. 431 

SECTION III. Universal Mill Plates: 

1. The 48" Mill at Homestead as an Example of Universal 

Plate Mills. 431 

2. The Operation of Rolling. 432 

3. Straightening, Marking and Shearing U. M. Plate.... 433 

4. Advantages of Universal Mill Plates. 433 

5. Physical Properties of Plates. 433 

6. Inspection of Plates. 434 


CHAPTER VIII. The Rolling of Large Sections. 


SECTION I. Railroad Rails: 

1. Development of Rail Manufacture. 436 

2. Methods of Rolling Rails. 437 

3. How to Study Roll Design. 438 

4. Precautions to be Observed in Designing the Rolls... 438 

5. Stages of Reduction. 439 

6. The Different Steps in the Design of the Rolls. 439 

a. The Section. 439 

b. The Cold Templet. 439 

c. The Hot Templet. 441 

d. The Pass Templet.^ 441 

e. Preparation for the Rolling. 443 

7. The Diagonal Method. 447 

8. The Mills. 447 

9. Rolling Heavy Rails. 448 

10 Unavoidable Variations. 448 

11. The Various Steps in Shaping of Rails. 449 

12. Cutting. 450 

13. Recording. 451 

14. Finishing and Inspection. 451 

15. Light Rails. 452 









































TABLE OF CONTENTS xxxi 


SECTION II. The Shaping of Rail Joints: 

1. Rolling Rail Joints. 454 

2 . Methods of Finishing Rail Joints. 458 

a. Cold Worked Bars. 459 

b. Cold Worked and Annealed Bars. 459 

c. Hot Worked Bars. 460 

d. Hot Worked and Oil Quenched. 461 

3. The Edgar Thomson Splice Bar Shop. 458 

SECTION III. Structural and Other Shapes: 

1 . Plan of Study. 461 

2 . Angles, Methods of Rolling. 462 

a. The Three Methods Compared . 462 

3. The Channel. 464 

4. Beams, Ties, and Piling. 464 

5. Zees and Tees. 466 

6 . Finishing Sections. 466 

7. Rounds. 467 

8 . Cutting and Straightening Rounds. 468 

9. Flats. 468 

10. Hexagons. 469 

11 . Deformed Bars. 469 

CHAPTER IX. The Rolling of Strip and Merchant Mill Products 

✓ 

SECTION I. Strip, or Hoop, Mills and Their Products: 

1. Meaning of the Word Hoop. 470 

2. Hoop as a Rolling Specialty. 470 

3. The Carnegie Hoop Mills. 470 

4. Methods of Rolling Hoop. 471 

5. Precautions Required in Rolling Hoop. 471 

6 . Finishing Hoop. 473 

SECTION II. Merchant Mills: 

1 . What the Merchant Mill Is. 474 

2. Kinds of Merchant Mills. 474 

a. The Guide Mill. 475 

b. The Belgian and Looping Mills. 477 

c. The Semi-continuous or Combination Mill.-... 477 

d. The Cross Country Mill. 479 

3. Future Development.'. 479 

SECTION III. Designing Rolls and Making up Schedules 

for Merchant Mills: 

1. Roll Designing for Merchant Mills. 482 

2. Economic Features of Roll Designing. 482 

3. The Order in the Office.. - 484 

4. The Order at the Mill—Size of Billet or Bloom- 486 








































XXXI1 


TABLE OF CONTENTS 


SECTION IV. Rolling Practice in Merchant Mills: 

1 . The Roller—His Importance. 487 

2. Precautions in Rolling. 487 

3. Rolling Defects. 488 

4. Two Different Finishes. 489 

a. Common Finish. 489 

b. Special Finish. 489 

SECTION V. Shearing and Bundling Merchant Mill 

Products: 

1 . The Methods of Shearing and Bundling. .... 490 

2 . Duties of the Shear Foreman. 490 

3. Bundling Export Material.. v . 491 

4. Special Bundling. 491 

5. Handling the Material in the Warehouse. 491 

6 . Straightening. 492 

7. Invoicing. 492 

SECTION VI. Inspection Department of a Merchant Mill 

Plant: 

1. The Inspection Department. 493 

2 . Function of the Inspection Department. 493 

3. Surface Defects. 494 

a. Buckles and Kinks..... 494 

b. Fins. 494 

c. Underfills. 494 

d. Slivers. 494 

e. Laps. 494 

f. Seams. 494 

g. Burned Steel. 495 

h. Roll Marks. 495 

i. Finish. 495 

j- Pipe. 495 

4. Testing for Defects. 495 

5. Other Duties of Inspectors. 495 

6 . Manner of Gauging Different Sections.. 496 

CHAPTER X. Circular Shapes. 

SECTION I. Some General Features Pertaining to the 

Rolling of Circular Shapes: 

1 . The Rolling of Circular Shapes. 497 

2 . Preparing the Blanks. 497 


































TABLE OF CONTENTS xxxiii 


SECTION II. The Carnegie Schoen Method for Manu¬ 
facturing Steel Wheels: 

1. The Carnegie Schoen Method. 498 

a. Forging the Blanks: 

i. First Method of Forging. 499 

ii. Second Method of Forging. 500 

b. Rolling the Forged Blank: 

i. The Rolling Mill. 500 

ii. The Rolling Process..... 503 

iii. Effect of the Rolling. 504 

c. Punching Web Holes and Coning. 504 

d. Inspection of Carnegie Schoen Wheels. 504 

e. Heat Treating Car Wheels. 506 

2. The Forging of Circular Shapes. 507 

CHAPTER XI. Forging of Axles, Shafts and Other Round 

Shapes. 

SECTION I. Howard Axle Works as an Example of a 

Forging Shop: 

1. The Plant and its Equipment. 508 

2. Precautions to be Observed in the Manufacture of Axles 508 

3. Inspection of the Blooms. 509 

4. Heating the Blooms. 509 

5. The Rolling and Forging Operation. 509 

a. Advantages of the Method. 510 

SECTION II. Finishing Processes for Forgings: 

1. Straightening.. .. 511 

2. Cutting-off and Centering. 511 

3. Rough Turning. 512 

4. Hollow Boring. 512 

a. Piping and Segregation. 512 

b. Strength and Weight. 512 

c. Hollow Boring and Heat Treating. 513 

5. The Heat Treating Plant. 513 

a. The Furnaces. 513 

b. The Quenching Tanks. 514 

c. The Testing Equipment. 515 

d. Advantages of Heat Treating Axles. 515 



































XXXIV 


TABLE OF CONTENTS 


PART III. 

THE CONSTITUTION, HEAT TREATMENT 
AND COMPOSITION OF STEEL. 

1. Introductory . 516 

CHAPTER I. The Constitution and Structure of Plain Steel. 

SECTION I. Steel as an Alloy of Iron and Carbon: 

1 . The Constituents of Steel. 518 

a. Ferrite. 518 

b. Cementite. 518 

c. Pearlite. 520 

2. Manner of Freezing of Solutions and Alloys. 520 

a. An Example of the First Class of Solutions... 520 

b. Example of the Second Class of Solutions—Salt 

and Water. 521 

c. Lead and Tin Solutions as Another Example of 

the Second Kind of Freezing. 523 

d. The Iron-Carbon Eutectic. 524 

i. Formation of Pearlite and the Eutectoid. . 525 

3. Structural Composition of Slowly Cooled Steel. 526 

a. Effect of the Constituents Formed Upon the 

Physical Properties. 526 

SECTION II. Thermal Critical Points of Steel: 

1 . Nature of Critical Points or Ranges of Steel. 527 

2 . Thermal Critical Point for Eutectoid Steel. 527 

3. Thermal Critical Points for Pure Iron. 528 

4. Thermal Critical Points of Low Carbon Steel. 528 

5. Thermal Critical Points of Medium Carbon Steel... 528 

6 . The Carbon-Iron Diagram for Steels and Methods 

of Notation.. 529 

7. The Position of the Critical Ranges. 530 

8 . Changes at the Thermal Critical Points. 530 

a. Changes at A 3 . 530 

b. Changes at A 2 . 531 

i. The Magnetic Properties. 531 

c. Changes at A 3,2 . 531 

d. Changes at Ai. 531 

9. Causes of the Thermal Critical Points in Steel. 532 



























TABLE OF CONTENTS 


XXXV 


SECTION III. The Crystalline Structure of Steel: 

1. Crystals and Grains. 533 

2. Crystallization of Steel: 533 

a. Crystallization of Eutectoid Steels. 534 

b. Crystallization of Hypo-Eutectoid Steel. 534 

c. Crystallization of Hyper-Eutectoid Steels. 535 

d. The Effect of Work on Grain Size. 535 

e. Crystalline Changes on Heating Steel: 535 

i. Crystalline Refinement on Heating. 536 

3. Practical Importance of Grain Structure. 537 

4. Summary of Chapter I. 538 

CHAPTER II. Heat Treating Theory and Practice. 

Introduction. 539 

SECTION I. Annealing: 

1. The Annealing Operation. 539 

2. Purpose of Annealing. 539 

3. True Annealing and “Process” or “Works” Annealing 540 

4. Heating for True Annealing: 540 

a. Importance of Time in Heating for Annealing. . 542 

5. Cooling. 542 

a. Effect of Cooling on the Net-Work. 543 

b. The Effect of Cooling Upon Pearlite. 543 

c. Other Factors. 545 

d. Methods of Cooling. 545 

e. Combination Methods of Cooling. 545 

6. Double Annealing. 546 

7. Box Annealing. 546 

8. Annealing Hyper-Eutectoid Steels. 547 

9. Normalizing and Spheroidizing. 547 

SECTION II. Hardening: 

1. The Hardening Operation. 548 

2. Heating for Hardening. 548 

3. Cooling for Hardening. 549 

a. Cooling or Quenching Media. 551 

b. Combination Methods of Quenching. 551 

c. Manner of Quenching. 553 

4. Progressive Hardening. 553 

5. Hardening Eutectoid Steels. 553 

6. Hardening Hyper-Eutectoid Steels. 553 

7. Hardening Hypo-Eutectoid Steels. 554 




































XXXV L 


TABLE OF CONTENTS 


SECTION III. The Tempering of Hardened Steel: 

1. The Tempering Process. 554 

2. Nature and Theory of Tempering. 555 

3. Methods of Determining Tempering Temperatures. 556 

4. Influence of Time in Tempering. 557 

5. Physical Properties Affected by Tempering. 557 

6. Tempering the Steels of Different Structural 

Composition. 557 

a. Tempering Austenitic Steels. 558 

b. Tempering Martensitic Steels. 55S 

c. Tempering Troostitic Steels. 558 

d. Sorbite. 559 

SECTION IV. TiiE Toughening of Steel: 

1. Toughening Defined. 559 

2. Benefits of Toughening. 559 

3. Quenching for Toughening. 559 

4. Change of Constituents Due to Toughening Fig. 118.. 560 

5. Physical Properties of Toughened Steel Tab. 62. 561 

SECTION V. Case Hardening: 

1. The Process of Carburizing Iron.. 562 

2. Application of Case Hardening. 562 

3. The Two Periods of the Case Hardening Process. . .. 562 

4. Kinds of Steel Suitable for Case Hardening. 563 

5. Case Hardening Properties of the Elements: 

a. Carbon. 563 

b. Manganese. 563 

c. Silicon. 563 

d. Phosphorus and Sulphur. 563 

e. Nickel. 563 

f. Vanadium. 563 

g. Chromium.•. 564 

6. The Carburizing Agent. 564 

7. Carburizing Materials:. 564 

a. Packing and the Action of Charcoal Carburizer 564 

b. Carburizing Mixtures and Compounds. 565 

8. Heating the Carburizing Pack. 566 

a. Controlling the Temperature. 567 

9. Removal of the Articles from the Boxes After 

Carburizing.. ... 567 

10. Heat Treatment of Case Hardened Articles. 568 

11. Superficial Hardening. 568 


































TABLE OF CONTENTS xxxv ii 


CHAPTER III. Constituent Elements of Commercial Carbon 

Steel and Their Influence Upon Its 
Mechanical Properties. 

Introductory. 559 

1. Properties of Iron. 509 

2 . Effect of Carbon. 579 

3. Influence of Manganese. 570 

a. Influence of Manganese in Heat Treatment... 571 

b. Influence of Manganese on Sulphur. 572 

4. Influence of Sulphur. 572 

a. Why Manganese Neutralizes Effect of Sulphur. 572 

b. Uses for Sulphur in Steel. 572 

5. Influence of Phosphorus. 573 

a. The Two Evils of Phosphorus. 574 

6 . Influence of Silicon. 574 

7. The Influence of Oxygen. 575 

8 . Combined Effect of the Elements on Tensile Strength 

of Steel. 575 

9. The Influence of Copper. 576 

10 . Influence of Tin. 577 

11. Influence of Arsenic. 577 

CHAPTER IV. Alloy Steels. 

SECTION I. Introductory'. 

1 . Definitions. 578 

2 . Carnegie Types and Grades. 579 

SECTION II. Nickel Steel: 

1 . Manufacture of Simple Nickel Steel. 580 

2 . The Different Nickel Steels and Their General 

Characteristics. 5S1 

3. Reasons for These Peculiarities of the Nickel Steels. . 582 

4. Structural Changes Due to Nickel. 584 

a. Pearlitic-Nickel Steels. 584 

b. Martensitic-Nickel Steels. 584 

c. Austenitic-Nickel Steels. 584 

5. The Constitutional Theory of Ternary Steels. 584 

6 . Heat Treating Pearlitic Nickel Steels. 585 

SECTION III. Chrome Steel: 

1 . The Manufacture of Simple Chromium Steels. 587 

2 . Influence of Chromium. 587 

a. The Microscopic Constituents of the Chrome 

Steels. 588 

3 . Uses of the Simple Chrome Steels. 589 

4. Heat Treatment of Chrome Steel.. 589 




































XXXV1U 


TABLE OF CONTENTS 


SECTION IV. Chrome — Nickel Steels: 

1 . Influence of Chromium and Nickel When Combined. 590 

2. Types of Chrome-Nickel Steel. 590 

3. Mayari Steel. 591 

4. Uses of Chrome-Nickel Steels. 591 

5. Heat Treatment of Chrome-Nickel Steels. 592 

G. Physical Properties of Chrome-Nickel Steels. 593 

SECTION V. Vanadium Steels: 

1. Simple Vanadium Steels. 595 

2 . Influence of Vanadium. 595 

SECTION VI. Chrome-Vanadium Steels: 

1 . Effect of Combining Chromium and Vanadium. 596 

2. Properties and Uses of Chrome-Vanadium Steels. 596 












PART 1. 

THE MAKING OF STEEL. 

CHAPTER 1. 


SOME FUNDAMENTAL PRINCIPLES OF PHYSICS AND 

CHEMISTRY. 

SECTION 1. 

INTRODUCTION. 

L Hon, the Master Metal: In beginning this very brief study 
of the metallurgy of the most important metal of a metallic age, it is difficult 
to refrain from pointing out a few of the qualities that have made iron the 
master metal, although its importance really needs no comment here. A 
little reflection shows it to be as vital to modern civilization as air and water 
are to life; and it has become so common that, like air and water, its true 
importance is lost sight of by most people, who look upon its abundance as 
a matter of course and value it accordingly. No other one metal has contributed 
- so much to the welfare and comfort of man. There is scarcely an article 
used in our daily lives that has not been produced from iron or by means 
of it. Consider bread as an example. Plows made of iron turn the soil, 
harrows of iron level it, and drills of iron sow the seed; machines of iron harvest 
the wheat and thrash it;,rolls of iron crush the grain to separate the flour; 
engines of iron bring the flour to our homes, where it is made into dough in 
iron pans and baked in an iron stove; finally the bread is sliced from the loaf 
with an iron knife, and served to us at a table made with iron tools. It has no 
exact substitute in nature, and without it most of our modern conveniences 
would have been impossible of development. The railroads, the automobile, 
and the watch are three of the many notable examples of such conveniences 
No other metal is capable of giving the great range in physical properties, 
that makes iron available for an almost unlimited number of purposes. Thus, 
from our towering skyscrapers, our massive bridges and our immense ships, 
where, as great beams, cables and plates, it supports loads almost greater 
than the mind can conceive, we can trace it even to our parlors, where, as 
invisible hairpins, it supports milady’s tresses and, as the strings of her piano, 
sends forth at her magic touch sweet sounds of melody. One property which 
it possesses in a far greater degree than any of the other metals is that of 
magnetism. This property is so pronounced in iron and so slight in other 
metals that, from a practical viewpoint, iron and one of its compounds may 
be considered as the only magnetic substances. Hence, our modern magnetic 


2 


METALLURGY , MATTER 


and electrical appliances are dependent upon this one metal; and we find 
it forming the essential parts of the dynamo, the electric motor, the telegraph, 
the telephone, the wireless telegraph, the compass, and a large number of other 
instruments of less importance. And so we might continue at great length 
upon this one topic of the importance of iron, but our time is too short to 
permit our giving much of it to a theme which the reader may develop for 
himself. Hastening on, then, to more important matters, we find the first 
question that confronts us is, What is Metallurgy? 

Metallurgy: In general, Metallurgy is defined as the science which 
deals with the preparation of the metals and their adaptation to the uses 
for which they are intended. It is an advanced and specialized science, 
hence a difficult one. Even a slight understanding of the subject requires 
a previous knowledge of the fundamental sciences of Physics and Chemistry. 
For those who may not have had the necessary preparation in these pre¬ 
requisites, this study is becomingly introduced by a brief consideration of 
some of the more important principles of these two sciences. To present 
these principles in as concise and simple a manner as possible is the object 
of this chapter. 

Matter: Through the various senses of sight, touch and hearing, the 
human intellect becomes aware of the existence of things which, collectively, 
are called matter. Matter contained in a limited portion of space is 
termed a body, and the different kinds of matter are, in general, spoken 
of as substances. Matter is a fundamental thing and cannot be accurately 
defined. It is described by its properties, which will be discussed later. 

The Fundamental Law and the States of Matter: Certain facts 
about matter, however, are plainly evident. It occupies space, and can 
be neither increased nor decreased in amount. These last two facts are 
commonly known as the Law of the Conservation of Matter. It exists 
in any one of three states; solids, which have definite masses, sizes and 
shapes; liquids, which have definite masses and sizes but not form; and gases, 
which possess definite masses only. A common example is water, which 
at ordinary temperatures exists in all three states; namely, ice, water and 
vapor. Liquids and gases together are called fluids on account of their 
flowing properties, and in many instances they are'subject to the same laws. 
They are distinguished from each other by their relative compressibility. 
Liquids are but slightly compressible, while gases are highly compressible. 
The volume of a gas varies inversely as the pressure applied to it. For 
example, if a certain mass of gas has a volume of 10 cu. ft. under a pressure of 
100 lbs., the same mass of gas will occupy but 5 cu. ft. at 200 lbs. pressure. 

Molecules: Furthermore, while the conception may seem difficult to 
establish as a fact, there are strong reasons for believing that the relatively 
large bodies, in which form matter makes itself evident to the human 
senses, are composed of minute particles, called molecules. This belief is 




MOLECULES 


3 


founded upon many facts, and can be arrived at by some such process of 
reasoning as follows: Mental conception concerning the constitution of 
matter may be based on either one of two hypotheses; namely, that matter 
is infinitely divisible or that it is made up of small particles. According 
to the first hypothesis, a body of matter could be divided indefinitely, if 
means were available to make such a process possible, without changing 
any of its characteristics, except its size; that is, a piece of chalk, for 
example, would remain chalk even as the particles resulting from the infinite 
division approached zero in size and weight. This retention of original 
characteristics would imply that each individual kind of matter, the chalk 
in the present instance, is an elementary substance. But this conclusion 
is contrary to the facts, for it is a matter of common knowledge that many 
substances like iron ore, limestone, sugar, etc., are composed of substances 
quite different from the original. Thus, through the application of heat 
alone, limestone and sugar are decomposed, the former into quick lime 
and carbonic acid gas, and the latter into carbon, or charcoal, and water. 
Only the second hypothesis remains, and it agrees with these facts, for it 
assumes that the larger masses of limestone and sugar, so evident to our 
senses, are made up of small particles, each of which is composed of 
portions of these simpler things into which the limestone and sugar are 
decomposed by the heat. These ultimate particles of the different 
substances are called molecules, which are, therefore, defined as the 
smallest particles of a substance that retain the characteristics of that 
substance. 

Sciences of Matter: Two great classes of matter are evident; animate 
or living matter, such as the living bodies of plants and animals, and 
inanimate matter, such as glass, water, air, etc. Animate matter is treated 
of by the sciences of Biology, Zoology and Botany; inanimate, by Physics 
and Chemistry, formerly included under the one head of Natural Philosophy. 
Thus, Metallurgy may be looked upon as a highly specialized branch of 
Natural Philosophy. All these sciences are so closely related that a 
knowledge of all is essential to a complete understanding of any one. 


SECTION II. 

SOME PHYSICAL PROPERTIES OF MATTER. 

Properties: That a better understanding of matter may be obtained 
from a study of its properties has already been indicated. By properties 
is meant those characteristics by which the different kinds of matter are 
distinguished and by which it may be described and defined. They are 
of two classes,—namely, general and special. General properties are 
common to all matter, while special properties are peculiar to certain kinds 
of matter only. The general properties are as follows: 

Inertia: This property causes matter to resist any attempt to change 
its state of rest or motion. 



4 


PHYSICAL PROPERTIES 


Extension is that property by virtue of which matter occupies space. 
There are two systems of measuring extension, the English and the metric. 
In the English system, the linear unit is the yard, while the volumetric 
units, as established by custom, are the gallon, the bushel, and the cubic 
yard. Corresponding units in the metric system are the meter=l.09361 
yards=39.37 inches; the kilometer—.62137 mile; the liter=.26417 gallon= 
1.0567 quarts, liquid, or .908 quart, dry; and the cubic meter=1.30S cubic 
yards. 

Mass, commonly taken as the amount of matter in a body or as the 
measure of its inertia, is an inherent property of any body, independent of 
the kind of matter of which the body is composed and of its position with 
reference to other bodies. These facts distinguish it from weight, which 
is defined as the force with which a body is attracted to the earth. The 
metric unit is the gram, practically equivalent to a cubic centimeter of 
water at 4°C. For commercial purposes the kilogram=1000 grams=2.20462 
pounds avoirdupois is the unit used. 

Density is the weight or mass of a unit volume of matter. It is usually 
expressed in grams per cubic centimeter. 

Specific Gravity is the number of times a body is heavier than an 
equal volume of some substance used as a standard. For liquids and solids 
this standard is water; for gases it is air or hydrogen. In the metric system 
density and specific gravity are numerically the same, since the weight of 
one cubic centimeter of water is one gram. 

Porosity: All matter is porous. The molecules, it is thought, are 
separated, even in the densest materials, by spaces larger than the mole¬ 
cules themselves. 

Impenetrability: Two bodies of matter cannot occupy the same space 
at the same time, and to this property of matter the term impenetrability 
is applied. 

Special Properties: The chief special properties of matter, some of 
which are of supreme importance in the manufacture of steel, are as follows: 

Cohesion and Adhesion: According to the law of gravitation, every 
particle of matter in the physical universe attracts every other particle 
with a force whose direction is that of a line joining the two particles and 
whose magnitude varies directly as the product of the two masses, and 
inversely as the square of the distance between them. Applied to molecules, 
this attraction is known as cohesion and adhesion; the former is the 
attraction of molecules of the same kind for each other, the latter, the 
attraction of unlike molecules. The clinging of a drop of water to the end 
of a glass rod exemplifies both of these forces. 

Elasticity is the power of matter to assume its original shape after 
having been distorted. The property of cohesion causes all bodies to resist 
change in form, but only solids have elasticity of form. When a solid body 




PHYSICAL PROPERTIES 


5 


is deformed, the resistance it offers is called the stress; the deformation 
which produces this stress is called the strain. Hooke’s law states that, 
up to the elastic limit, the strain is proportional to the stress. In practice, 
the stress is measured in terms of a force or forces applied externally 
to the body being tested. There are four methods of calling forth the 
elasticity of bodies:—namely, by pressure, by stretching, by bending and 
by twisting. Stretching and bending are the methods most commonly 
employed in testing the elasticity of steel. 

Plasticity is the opposite of elasticity. A plastic body once distorted’ 
will not regain its original shape. 

Ductility is sometimes defined as the property by virtue of which 
matter may be drawn into fine wires. As the term is employed in the 
testing of steel, ductility is the distortion or strain a body undergoes in 
being ruptured. 

Malleability: Some kinds of matter, metals in particular, can be 
hammered or rolled into thin sheets. This property is called malleability. 

Hardness is the ability to withstand abrasion, or resist penetration. 

Crystallization: Some substances in changing from a liquid to a solid 
form, separate not as a continuous compact mass but as bodies having a 
definite shape and color, called crystals. That crystals may form, it is 
necessary that the molecules be free to arrange themselves in a definite 
order. This condition is secured when a substance is in solution or in a 
molten state. In steel manufacture this property is of great importance. 

Diffusion is most characteristic of liquids and gases. It is the property 
that causes two fluids in contact to intermingle. Liquids diffuse slowly, 
but gases much more rapidly. 

Effusion is the term applied to that property of gases which causes 
them to pass through porous solids. The rates of effusion of different gases 
is inversely proportioned to the square roots of their relative weights. 

Absorption: Many porous bodies, like coke, charcoal, platinum 
sponge, etc., are capable of absorbing large quantities of gases. Thus, 
one cubic centimeter of charcoal is capable of absorbing from thirty to 
thirty-five times its own volume of carbon dioxide. Gases are condensed 
on the surface of all solids, and porous bodies offer a large surface for con¬ 
densation. 


SECTION III. 

ENERGY, HEAT AND TEMPERATURE, AND THE ETHER. 

Energy: Physics and Chemistry, however, have to do with more than 
matter. The senses also reveal the presence of a second factor in nature, 
called energy. Like matter, energy is a fundamental that cannot be 
satisfactorily defined. It is not a thing. It is that which gives a body 
the ability to move against a resistance; that is, the ability to do work. 




6 


ENERGY AND HEAT 


Thus, a body may possess energy and still neither move nor do any work. 
Like matter, energy is conserved. It may be changed from one form to 
another or be transferred from one point to another, but the total energy 
of the Universe remains constant. This fact is known as the Law of Con¬ 
servation of Energy. 

Kinds of Energy: There are two kinds of energy; namely, potential 
or stored up energy, sometimes called energy of position, and kinetic energy, 
or the energy possessed by a body by virtue of its motion. Thus, a weight 
on the top of a building possesses potential energy with respect to the 
ground by virtue of its position; if it is permitted to fall, its energy then 
becomes kinetic. Energy is measured in terms of the work which it is 
capable of doing. 

Heat and Temperature: One form of energy is heat. Heat must 
not be confused with temperature. The latter measures one of the effects 
of the former. The difference may be illustrated thus:—Let it be supposed 
that two portions of natural gas, each of a cubic foot, are burned completely, 
so that the heat liberated is entirely absorbed by two bodies of water 
initially at the same temperature, the volumes of which are a quart and 
a gallon, respectively. It is evident from common experience that the 
temperature of the smaller portion of water will be raised the higher, though 
the quantity of heat imparted to each is precisely the same. 

Effects of Heat: Heat produces marked effects on matter. All matter 
expands by the application of heat alone, though there are many apparent 
exceptions. The volume of a gas varies directly as the absolute temper- 
ature. other conditions remaining constant. Change of state may be 
caused by heat. Thus, glass or iron, dense solids at ordinary temperatures, 
readily assume the fluid state on being heated above their fusion point. 
According to the kinetic theory of heat, the molecules of matter always 
have a certain amount of independent motion, and the effect of adding 
heat is to increase the energy of this motion, the molecules being thereby 
forced farther and farther apart. This forcing apart of the molecules 
accounts for the change of state as well as the expansion of bodies on being 
heated. 

Temperature is determined by measuring the expansion it produces in 
a volume of mercury enclosed in a small glass tube, called a thermometer. 
The length of the tube is marked off into small divisions, which constitutes 
the scale of the thermometer. There are four thermometer scales in 
common use; the Centigrade, Fahrenheit, Reaumur and Absolute. The 
difference among them consists of the number of divisions between the 
freezing point and the boiling point of water, and the numbers applied to 
these divisions. 

The Centigrade is the thermometer employed in all scientific work. 
]n it the freezing point is marked zero and the boiling point 100°. The only 




ENERGY AND HEAT 


7 


difference between this scale and the Absolute is that, in the latter, the 
zero point is 273° below the Centigrade zero. 

In the Fahrenheit thermometer, the space between the freezing and the 
boiling points is divided into ISO equal parts, and zero is 32 of these parts 
below the freezing point of water. The boiling point, therefore, is 212°. 


In the Reaumur scale, the 
freezing point is marked zero 
and the boiling point 80°. For 
high temperatures, instruments 
called pyrometers are used. 

These relations of the 
various scales are shown in the 
accompanying diagram: From 
this diagram the following for¬ 
mulas are readily developed: 

Temp. A=Temp. 0+273. 

Temp. C=Temp. A—273. 

Temp. F=Temp. %C+32. 
Temp. C=Temp. (F—32°)%. 



Fig. 1. Diagram showing relations of the 
various thermometer scales. 


Measurement of Heat: Heat is measured in calories. A calorie (cal.) 
is the heat required to raise the temperature of one gram of water one 
degree centigrade. In practice the large calorie (Cal.) is employed. It 
is the amount of heat required to raise one kilogram of water through 
one degree centigrade. The corresponding unit in the English system is 
the B. t. u. (British thermal unit), which is the heat required to raise 
the temperature of one pound of water one degree Fahrenheit. These units 
may be converted from one to the other by use of the following factors: 

1 Calorie=3.96S B. t. u. or 
1 B. t. u.= .252 Cal. 


The Ether: A third factor composing the Universe is the Ether. 
Little is known about it except that it fills all space, permeates all matter 
and transmits light, heat, and electric waves. Its properties are very 
difficult to analyze, because the senses are not directly affected by it. Its 
presence was first suspected through the study of the transmission of light. 
By comparatively simple experiments, it was shown as early as 1802 that 
light is transmitted by a wave motion, and since light is transmitted through 
a vacuum, something other than matter must act as the medium. The 
same conclusion is arrived at by a study of heat radiation. The develop¬ 
ment of wireless telegraphy was based on this supposition, and its success 
is further evidence of the existence of the Ether. 

















s 


CHANGES IN MATTER 


SECTION IV. 

CHANGES IN MATTER. 

Physical and Chemical Changes: Matter is constantly undergoing 
changes. A close observer soon discerns that these changes are of two 
kinds,—namely, one in which the nature and composition of the matter 
undergoing the change remains the same, called a physical change, and 
another in which the nature and composition are affected, called achemical 
change. The bending of a stick, the freezing of water, the fusion of steel 
are examples x)f the former, while the burning of coal is a common example 
of the second. In many physical changes and in all chemical changes heat 
is involved,—being either absorbed or liberated. Chemical changes that 
liberate heat furnish a source of energy— chemical energy. 

The Make=up of Material Bodies: In considering the make-up of 
the various bodies of matter, it is necessary to distinguish bet ween mere 
mixtures and more closely combined substances. A mechanical mixture 
is a mixture of two or more substances, which is not homogeneous and the 
constituents of which can be separated by mechanical means. Such mix¬ 
tures are made up of molecules of different kinds. A chemical compound 
is homogeneous throughout its mass, and its constituents cannot be separat¬ 
ed by mechanical means, that is, its molecules are all of the same kind. The 
components of any given chemical compound are always in the same pro¬ 
portions for that compound. This fact distinguishes compoimds from 
alloys and solutions which, though they are practically homogeneous and 
sometimes are practically impossible of separation by mechanical means, 
are never constant in composition. An alloy is a metallic substance, the 
components of which are wholly or partly soluble in each other in the liquid 
state. 

Kinds of Chemical Compounds: A close study of a great number 
of chemical compounds will show that all substances fall into four classes; 
namely, acids, bases, salts and non-electrolytes. 

Acids are characterized by the fact that they all have a sour taste 
when in water solution and change the color of certain chemicals, called 
indicators. One of the most common of these indicators is litmus, of 
which there are two colors, a blue and a red. Acids change the color of 
blue litmus to red. Vinegar is chiefly a dilute solution of acetic acid. 

Bases have the power of neutralizing acids, and may be looked upon 
as their opposites. Examples are quick lime, lye, etc. Bases change the 
color of red or neutral litmus to blue. 

A Salt is the product formed when an acid is neutralized by a base. 
Common table salt, made by neutralizing hydrochloric acid with sodium 
carbonate, is an example. As a rule acids, bases, and salts are electrolytes, 
that is, their water solutions will conduct the electric current. 

Non Electrolytes: There are some compounds that do not resemble 
either acids or bases, nor can they be classed as salts. They are char¬ 
acterized by the fact that their water solutions will not conduct the electric 
current, so are termed non-electrolytes. Benzene, methane and distilled 
water are examples. 





CHANGES IN MATTER 


9 


Chemical Elements: Notwithstanding the fact that chemical com¬ 
pounds are homogeneous and camiot be separated by mechanical means, 
they are readily divided into simpler substances by chemical processes. 
These simpler substances are called elements, and each and every chemical 
compound is composed of two or more chemical elements. While the 
number of chemical compounds is almost unlimited, there are compara¬ 
tively few elements. In 1918, the discovery of 84 elements had been 
reported. The total number lies between 92 and 97. Of these, twelve 
compose about 99 per cent, of the earth’s crust. It has been estimated 
that the solid crust of the earth is made up approximately as follows: 

Oxygen. 49.85% Calcium. 3.18% Hydrogen.97% 

Silicon. 26.03% Sodium. 2.33% Titanium.....41% 

Aluminum. 7.28% Potassium. 2.33% Chlorine.20% 

Iron. 4.12% Magnesium...... 2.11% Carbon.19% 


TOTAL 99.00% 

Classification of Chemical Elements: A study of the elements 
reveals the fact that there are two great classes; namely, those that combine 
with oxygen and hydrogen to form bases, and those that combine with oxygen 
and hydrogen, or hydrogen alone, to form acids. The former are sometimes 
called metals and the latter non=metals, or metalloids. The line of 
division is not a sharp one. Some elements form both acids and bases, 
but the tendency is more pronounced in the one direction than in the other. 
Furthermore, like plants or animals, these two divisions may be sub-divided 
into families or groups, the members of which possess similar properties. 
These divisions and groups are shown in a subjoined table. 

Symbols: For convenience and brevity, each element is represented 
by a symbol. These symbols are composed of the first letter, capitalized, 
of the English or Latin names of the elements, combined, where necessary 
as a distinguishing mark, with some succeeding letter. Thus, C=carbon, 
Ca=calcium, Cd=cadmium, F=fluorine, Fe=ferrum (iron), etc. 

Fundamental Laws of Chemical Changes: Now, where the elements 
combine to form a compound they always do so in definite proportions 
by weight. Thus, fifty-six parts by weight of iron will combine with 
sixteen parts by weight of oxygen, or fourteen parts by weight of nitrogen 
with sixteen parts by weight of oxygen. This fact is known as the Law of 
Definite Proportions, and the definite weights are called combining weights. 
Further investigation along this line shows that some pairs of elements form 
more than one compound and that the combining weights of the elements 
in these different compounds are simple multiples of each other. Concisely 
stated, the law is this: Whenever two elements unite to form more than 
one compound, if we consider a fixed weight of the one, the weights of 
the other which combine with it are integral multiples of one 
another. This fact is known as the Law of Multiple Proportions, or 
Dalton’s second law. The following compounds formed by the two 



















10 


ATOMS 


elements nitrogen and oxygen are well known examples: 


n Parts by Weight Parts by Weight 

Compound of Nitrogen of Oxygen 

Nitrous Oxide. 28 16 

Nitric Oxide. 28 32 

Nitrogen Trioxide. 28 48 

Nitrogen Peroxide. 28 64 

Nitrogen Pentoxide. 28 80 


SECTION V. 

THE ATOMIC AND ELECTRON THEORIES. 

Atoms: Upon the facts just stated in the preceding section, the 
English chemist Dalton founded a very important hypothesis, now known 
as the atomic theory. In order to explain the laws stated above, reasoning 
led to the following assumptions: 

1st: The molecules of matter are themselves made up of small particles. 

2d: These particles possess the power of attracting other particles or 
otherwise attaching themselves to them. 

3d: These particles do not subdivide in taking part in chemical changes. 

These particles are called atoms. All the atoms of the same element 
have the same mass or weight, the same form, and the same combining 
power, while atoms of different elements differ in one or more of these 
respects. 

Atomic Weights: The atom is so small that it is useless to hope that 
its mass or weight will ever be determined absolutely. However, the 
weight of one atom of an element must be proportional to the combining 
weight of that element. Since the combining mass or weight of hydrogen 
is the least of all the other elements, it is assumed that its atom is the 
lightest. Therefore, the atomic weight of hydrogen was made one by 
Dalton and the atomic weight of the other elements multiples of it. However, 
since hydrogen forms with other elements comparatively few compounds 
that can be used for atomic weight determinations and oxygen more than 
any other element, it was decided later to make the latter element the 
standard. Accordingly, the atomic weight of oxygen is made 16, and the 
atomic weights of other elements are compared with it as a standard,thus 
making hydrogen 1.008. This system of comparative weights is known as- 
the international table of atomic weights. 

Valence: Concerning the attractive power of the atoms of the various 
elements, it may be pointed out that the law of multiple proportions indicates 
that the atom of an element may combine with one or more atoms of another 
element in forming compounds with it. Here, again, hydrogen is used as 
a standard, for since its combining weight is the least of all the other 
elements, it is assumed that the holding power of its atoms must also 
be the least. Therefore, the valency of an atom is properly defined 
as the number of hydrogen atoms it is capable of combining with 
or replacing. The valencies of the atoms of the elements are by no 
means fixed quantities, but vary—in some cases from one to seven. 









ELEMENTS 


11 


The following table is intended to furnish a complete list of the elements, 
with their symbols and atomic weights, and to show, also, the classification 
and valencies of the more common ones. Very rare elements are placed 
in a separate list. Elements that ordinarily are both acid and basic 
are marked with an *, and those important in the manufacture of steel 
are printed in Italics. 

Table 1—The Chemical Elements. 


Showing Physical Constants of the More Common Ones. 


Class 

Group 

Name 

Symbol 


Potassium 

Lithium. 

Li 



Potassium . 

K 



Sodium . 

Na 


Calcium.. . 

Calcium . 

Ca 



Barium. 

Ba 



Glucinum. 

G1 



Strontium. 

Sr 


Magnesium 

Magnesium . 

Mg 



Zinc. 

Zn 



Cadmium. 

Cd 


Ri 1 v ft r 

Silver. 

Ag 

O 


Copper . 

Cu 

£ 


Mercury. 

Hg 









r v* 

Aluminum 

* Aluminum . 

Al 

hH 

O 


Gallium (rare).. . 

Ga 



Thallium “ 

T1 

w 


Scandium “ 

Sc 

m 




< 

1 jpi^.rl 

♦Lead. 

Pb 

i—i 


*Tin. 

Sn 


Chromium 

* Chromium . 

Cr 



* Molybdenum . 

Mo 



* Tungsten . 

W 


Manganese 

* Manganese . 

Mn 


Iron 

Iron . 

Fe 



Cobalt . 

Co 



Nickel . 

Ni 


Palladium. 

♦Palladium. 

Pd 



Ruthenium (rare) 

Ru 



Rhodium (rare).. 

Rh 


Gold 

♦platinum. 

Pt 



♦Gold. 

Au 


1921 

Atomic 

Weight 

Valence 

Specific 

Gravity 

Melting 

Point 

Boiling 

Point 

0=16 

Water 

Air 

°C 

°C 

6.94 

I 

.534 


186 

1400 

39.1 

I 

.851 

.... 

62.3 

710 

23.0 

I 

.952 


97.5 

750 

40.07 

II 

1.54 


810 


137.37 

II 

3.8 

.... 

850 

950 

9.1 

II 

1.85 

.... 

1280 


87.63 

II 

2.5 

.... 

830? 

. 

24.32 

II 

1.7 


651 

1120 

65.37 

II 

7.1 

.... 

419.4 

930 

112.40 

II 

8.6 

.... 

320.9 

778 

107.88 

I 

10.5 

.... 

960.5 

1955 

63.57 

I-Il 

8.9 

.... 

1083 

2300 

200.60 

I-II 

13.60 

.... 

-38.87 

357 

27.1 

111 

2.7 

.... 

658.7 

1800 

70.1 


5.95 

.... 

30 

2000 

204.0 


11.85 

.... 

302 

1280 

45.1 




14001 


207.2 

II-IV 

11.3 


327.4 

1525 

118.7 

II-IV 

7—7.3 

. . . . 

231.9 

2270 

52.0 

II-III-VI 

6.9 

.... 

1615 

2200 

96.0 

IIPIV-VI 

8.8 

.... 

2550 

3600 

184.0 

IV-V-VI 

18.8 

. . .. 

3400 

5800 

54.93 

II-IV 

7.4 

. .. . 

1230 

1900 

55.84 

1I-III 

7.86 


1530 

2450 

58.97 

I1-1II 

8.7 

.... 

1480 

. • • • . 

58.68 

II-1I1 

8.7 

. . .. 

1452 


106.7 

I-II-IV 

12.2 


1550 


101 7 


12.1 


24501 


102 9 


12.4 


1950 


195.2 

IV 

21.37 


1755 

3900 

197.2 

I-III 

19.3 

. • • . 

1063 

2530 














































































12 


ELEMENTS 


3 

o 


O 

£ 

H 

§ 

o 


Q 

O 

c 


Table I—The Chemical Elements—Continued. 


Group 

Name 

Symbol 

1920 

Atomic 

Weight 

Valence 

Specific 

Gravity 

Melting 

Point 

Boiling 

Point 

0—16 

Water 

Air 

°C 

°C 

Chlorine .. 

Fluorine . 

F 

19.0 

/ 

1.14 

1.31 

—223 

—187 


Chlorine . 

Cl 

35.46 

/ 

1.51 

2.49 

-101.5 

—37.6 


Bromine. 

Br 

79.92 

I 

3.1 

5.52 

—7.3 

59 


Iodine. 

I 

126.92 

I 

4.9 

.... 

113.5 

184 








/ 112.8 


Sulphur. . . 

Sulphur . 

5 

32.06 

11-1V-VI 

2.0 

.... 

^ 119.2 

444.6 








1 106.8 



Selenium (rare). . 

Se 

79.20 


4.3 

.... 

218.5 

690 


Tellurium “ 

Te 

127.50 


6.2 

.... 

452 

1390 

Carbon. . . 

Carbon . 

C 

12.0 

IV 

1.7-3.5 


Infusible 

3500 


Silicon . 

Si 

28.3 

IV 

2.42 

.... 

1420 

3500 


Boron. 

B 

10.9 

III 

2.54 

.... 

2250? 

3500 


Titanium . 

Ti 

48.10 

1.V 

4.15 


1800 


lSrif,T*np , p.ii 

Nitrogen 

N 

14.01 

I to V 


.97 

— 210 

— 196 


Phosphorus . 

P 

31.04 

II1-V 

1.8 


44 

290 


* Arsenic. 

As 

74.96 

III-V 

5.7 

.... 

850 

449.5 


* Antimony. 

Sb 

120.20 

III-V 

6.6 

.... 

630 

1460 


*Bismuth. 

Bi 

208.0 

III-V 

9.7 

.... 

271 

1485 


* Vanadium . 

V 

51.0 

III-V 

5.7 


1720 



Oxygen 

O 

16.0 

II 


1.10 

—218 

—183 




(15.97) 







Hydrogen 

H 

1.008 

I 


.07 

—259 

—252 




( 1 .) 







Very Rare Elements. 

Atomic Atomic 



Name 

Symbol Weight 


Name 

Symbol Weight 

51 

Argon. 

.. A 

39.9 

68 

Neon. 

Ne 

20.2 

52 

Caesium. 

.. Cs 

132.81 

69 

Niton. 

Nt 

222.4 

53 

Cerium. 

.. Ce 

140.25 

70 

Osmium. 

Os 

190.9 

54 

Columbium. . 

.. Cb 

93.1 

71 

Praseodymium 

Pr 

140.9 

55 

Dysprosium.. 

•• Dy 

162.5 

72 

Polonium. 

Po 

210.0 

56 

Erbium... . . . 

. . Er 

167.7 

73 

Radium. . . . . 

Ra 

226.0 

57 

Europium.... 

Eu 

152.0 

74 

Rubidium. 

Rb 

85.45 

58 

Gadolinium.. 

.. Gd 

157.3 

75 

Samarium , „ . . 

Sa 

150.4 

59 

Germanium.. 

.. Ge 

72.50 

76 

Tantalum. 

Ta 

181.5 

60 

Helium. 

.. He 

4.0 

77 

Terbium. 

Tb 

159.2 

61 

Ilolmium. .. . 

. Ho 

163.5 

78 

Thorium. 

Th 

232.15 

62 

Indium. 

. . In 

114.8 

79 

Thulium. 

Tm 

168.5 

63 

Iridium. 

. . Ir 

193.1 

80 

Uranium... 

U 

238.2 

64 

Krypton. 

.. Kr 

82.92 

81 

Xenon. 

Xe 

130.2 

65 

Lanthanum. . 

La 

139.0 

82 

Ytterbium.... „ 

Yb 

173.5 

66 

Lutecium. ... 

Lu 

175.0 

83 

Yttrium. 

Yt 

89.33 

67 

Neodymium. 

.. Nd 

144.30 

84 

Zirconium. 

Zr 

90.6 



















































































REACTIONS 


13 


Electrons: Until 1900 all the elements had resisted all efforts to 
break them up into simpler substances, and atoms were considered to be 
the smallest divisions of matter. With the discovery of radium and other 
radio-active substances, however, a new field for investigation was opened, 
and subsequent discoveries indicate that the atom is divisible. These very 
small particles are called electrons. It is thought that electrons, in some 
intimate relation to the Ether, are the fundamental particles of which all 
matter is composed. 

SECTION VI. 

CHEMICAL FORMULA AND REACTIONS. 

Chemical Formulas of Compounds: The method of representing the 
elements by symbols, together with the system of atomic weights, affords 
a convenient and concise method of representing chemical compounds, or 
to be more explicit, the molecules of chemical compounds. Thus, by 
analysis, water is found to be composed of hydrogen and oxygen in the 
proportion of eight parts of oxygen to one part of hydrogen by weight. 
These facts are completely expressed by the formula H 2 0, which indicates 
a molecule of a compound composed of two atoms of hydrogen and one 
atom of oxygen, or, since the atomic weight of hydrogen is 1 and of 
oxygen, 16, 2 parts of hydrogen to 16 parts of oxygen (1 to 8). Likewise, 
the formula Fe 2 03 represents a compound, the molecule of which is made 
up of 111.68 parts of iron to 48 parts of oxygen. 

Molecules of Elements: In studying chemical changes in which 
elements are set free, it is found that they are much more active at the 
instant of their liberation than afterwards, and are, therefore, said to be 
in the nascent state at that instant. This fact leads to the belief that 
the instant an element is set free from its compounds it exists in the atomic 
condition, but if there is nothing else present with which the atoms can 
combine, they combine with each other to form molecules of the element. 
This idea cannot be proven in the case of solids, but its correctness is easily 
shown in the case of gases. From many facts, Avogadro was able to show 
that equal volumes of all gases, under the same conditions of temper- 
ature and pressure, contain the same number of molecules. Hence, 
the molecular weight in grams of all gases give a constant volume of 22.32 
liters, called the gram-molecular volume. Now, the weight of 22.32 liters 
of oxygen=32 gms., of hydrogen, 2 gms., of nitrogen, 28 gms. Dividing 
these weights by the respective atomic weights of the elements, the quotient 
is 2 in each case. Hence, the molecules of these elements contain two atoms 
each, and the correct formulas for these elements are 0 2 , H 2 and N 2 , 
respectively. 

Chemical Equations: This system of symbols and weights also 
simplifies the representation of chemical changes. Suppose it is desired to 
represent the chemical change that takes place when a common substance, 
like coal for instance, burns. Coal is largely made up of carbon; the element 
which combines with it is oxygen in the air; an invisible gas, C0 2 , is 





14 


REACTIONS 


formed and diffuses into the air. This change, spoken of as a reaction, 
is represented in the form of an equation; thus, C+ 0 =C 02 - 

Balancing Reactions: Since matter is conserved, there must be as 
many atoms on one side of the equation as on the other. This is shown by 
placing a 2 before O on the left side of the equation, thus, C+20=C02- 
This process is called balancing. Thus, reactions tell not only the names 
of the reacting substances and of the products formed, but also give the 
proportions by weight, and in the case of gases, volume relations as well. 

Radicals: In the molecules of many chemical compounds, certain 
groups of atoms appear to be more closely bound together than others in 
the same molecule. In these groups the atoms composing them appear to 
bear a fixed relation to each other, which remains unchanged during a 
chemical reaction. Thus, in many wet reactions in which H 2 SO 4 is 
employed as a reagent, the sulphur and oxygen do not separate but 
remain closely combined, as illustrated in the reaction that takes place 
between this acid and barium chloride: 


H 2 (S0 4 )+Ba Cl 2 =Ba (S0 4 )+2 HC1 
Such groups of atoms are called radicals. 


Ions and Electrolysis: In electrolytes these radicals are readily 
identified as ions. From a study of the effect of dissolved electrolytes on 
the boiling and freezing points of the water in which they are dissolved, 
and on their osmotic pressures, evidence is obtained to show that each of 
the dissolved molecules breaks up or dissociates into two or more parts. 



The following simple experi¬ 
ment may be employed to throw- 
additional light upon this sub¬ 
ject. Into the U-tube of Fig. 2 
is placed a solution of sodium 
sulphate and some neutral 
litmus, into which is immersed 
two small platinum rods to act 
as electrodes for an electric 
current, as shown in the figure. 
Upon closing the circuit, bubbles 
of hydrogen are given off at the 
cathode and bubbles of oxygen 
at the anode, while the solution 
about the cathode becomes deep 
blue in color, showing it is basic, 
and that about the anode be¬ 
comes red, showdng it to be 
acid. These facts are explained 
by assuming that the molecules 
























REACTIONS 


15 


of dissolved Na 2 S0 4 dissociate into parts, called ions. This 

+ + — 

dissociation is indicated thus: Na 2 S 04 =Na-f-Na-j-S 0 4 . The sodium 
ions, Na, carrying a positive charge of electricity, are propelled by 
the current toward the cathode, while the negatively charged sulphions, 
S0 4 , go to the anode. Here they give up their charges and become 
chemically active, decomposing the water thus: 

2 N a+ 2 H 2 0 = 2 Na 0 H+H 2 2S0 4 +2H 2 0=2H 2 S0 4 -f 0 2 

This experiment is but one example of electrolysis. Any inorganic acid, 
base or salt may be substituted for the sodium sulphate; and any conductor 
of electricity, such as iron, may be used instead of platinum. It is to be 
noted, however, that if iron had been used in this experiment, the anode 
would have been corroded away by the acid radical; thus, Fe+S0 4 = 
FeS0 4 . Electrolysis has been advanced to explain the corrosion of iron. 

Dry and Wet Chemistry: Chemical changes take place under constant 
conditions. Substances that will react in one way under one set of com 
ditions will not react, or react in an entirely different way, under another 
set of conditions. Some substances react simply by contact, as quick lime 
and water. Many reactions will take place only in a water solution, while 
many other substances, being insoluble in water, must be heated almost 
to their point of fusion before they react. A study of reactions between 
substances in solution is called “wet chemistry” while the study of reactions 
brought about by heat is termed ‘ dry chemistry.” However, under the 
same conditions, the same substances will always produce the same results. 
This fact is known as the law of constancy of nature. 

Acids, Bases and Salts of Dry Chemistry: Most substances dealt 
with in wet chemistry lose water when heated. This statement is par¬ 
ticularly true of inorganic acids, bases and salts. Thus, in the case of 
acids and bases, heat breaks up these compounds into water and oxides, 
called anhydrides. Acids give acid anhydrides, and bases, basic 
anhydrides. These anhydrides constitute the acids and bases of dry 
chemistry. They have the same power of neutralization that their 
corresponding wet compounds possess, and form neutral compounds to which 
the term slag is applied instead of salt. Many salts, in crystallizing from 
aqueous solutions, unite with, or better, take up a definite amount of water, 
which does not go to form a new compound, but to form crystals, and is 
called, therefore, water of crystallization. This water is held very loosely 
by the molecule and is readily given up by it. In some crystals, like those 
of washing soda, for example, this tendency is so pronounced that they give 
up their water of crystallization to the air, if its humidity is low. Such 
substances are said to be efflorescent. On the other hand, many dry 
substances absorb moisture from the air and are, therefore, said to be 




16 


REACTIONS 


hygroscopic. A few substances will absorb enough water from a very 
moist air to become wet and actually go into solution in the water they 
absorb. These substances are said to be deliquescent. The following 
reactions will serve to illustrate these facts in so far as they involve chemical 
changes: 

H 2 Si 03 +heat=H 2 0 -{-Si 02 
Metasilicic Acid Water Silica, or silicic anhydride 

Mg (0H) 2 +heat=H 2 0+Mg0 
Magnesium hydroxide Magnesia—a basic anhydride 


Na 2 S0 4 .10Ho0+heat=10H 2 04-Na 2 S04 
Glauber Salt Sodium Sulphate 

(Crystallized) (Dry Powder) 

In this connection a study of the following table will also prove helpful. 


Table 2. Acids, Bases and their Anhydrides with Salts 
Resulting from Neutralization. 


Name of Compound 

Formula of 

Formula of 

Salt With 

Compound 

Anhydride 

Univalent Base 

Divalent Base 

Trivalent Base 

Sodium hydroxide 
Calcium hydroxide 
Ferric hydroxide 
Sulphuric Acid 

Nitric Acid 

Orthophosphoric Acid 

Orthosilicic Acid 

NaOH 

Ca(0H ) 2 

Fe(OH)a 

H 2 S0 4 orHoO-SO a 

HNO ;{ or 

H-.O-NaO.-, 

H 3 P0 4 or 

SH 0 OP 2 O 5 

H 4 Si0 4 or 

2H 2 0-Si0 2 

Na.>0 

Ca'O 

Fe 2 0 3 

S0 3 

N 2 0 5 . 

P 2 O 5 

Si0 2 

Na 2 0 -S 0 ;i 0 r 

Na 2 S0 4 

NaoO-NoOoor 

NaNOa 

3NaoO-P->05or 

Na 3 P0 4 

2Na 2 0-Si0 2 or 

Na 4 Si0 4 

CaO-S0 3 or 
CaS0 4 
CaO-N->0.->or 
Ca(Nb : ,)-» 
(CaO) 3 ’P 2 0 r, 
orCa 3 (P0 4 ) 2 
(CaO) 2 -Si0 2 
orCa 2 Si0 4 

(Fe 2 0 3 ).(S0;«) 8 , 
orFe 2 (S0 4 ) a 
Fe 2 0 s - (N 2 Os)s 
orFe(N 03)3 
Fe 2 03 -P 2 05 
orFeP0 4 
FeoOalo* (Si 0 2 )3 
orFe 4 (Si0 4 ) 3 


Kinds of Reactions: As already indicated, all reactions may be placed 
under one of two heads; namely, those that liberate heat, called 
exothermic, and those that absorb heat, called endothermic. A more 
detailed classification, such as the following, is sometimes employed: 


1. Direct combination (synthesis)—2H+0=H 2 0 or 2H 2 +0 2 =2H 2 0. 

2. Direct decomposition (analysis)—2Hg0=2Hg-)-0 2 . 

3. Simple replacement or substitution—2H 2 0+2Na=2Na0H+H 2 . 

4. Double replacement or metathesis—BaCl 2 -j-H 2 S 0 4 =BaS 04 +2HC1. 
/3 Fe+40=Fe3C>4. 

'\Fe Cl 2 +Cl=Fe Cl 3 . 

/Fe 3 0 4 +8H=3 Fe+4II 2 0. 

"\Fe Cl 3 +H=Fe C1 2 +HC1. 

The two processes of oxidation and reduction are of great importance 
in metallurgy. They have a triple meaning. Primarily, oxidation means 
the taking on of oxygen by an element or compound, and reduction means 
the giving up of oxygen. In the case of elements that form more than one 


5. Oxidation- 


6. Reduction—< 























REACTIONS 


17 


compound, if the number of atoms of one that combines with a fixed number 
of the other be increased, the process is oxidation; if decreased, reduction. 
In metallurgy an element in the metallic state is said to be reduced. The 
two processes are inseparable; when one thing is reduced, another is 
oxidized. In metallurgical operations these two processes are of paramount 
importance, for all the substances reduced constitute the metallic product 
and all in oxidized form make up the slag. 

Some Laws Controlling Chemical Reactions: In writing reactions 
considerable knowledge of a specific character is essential. Thus, suppose 
it is required to write the reaction that represents the action of iron brought 
in contact with water. First, it will be necessary to know under what 
conditions the substances are brought together, for at ordinary temperatures 
no reaction will take place. At a high temperature, a reaction takes place, 
and it is necessary to know that ferroso-ferric oxide and hydrogen are 
produced, and the formulas of all these substances. This knowledge can 
then be indicated thus: Fe+H 2 0 =Fe 304 +H 2 . Balancing the reaction, 
which is done by inspection and arithmetic, is the next step. Finally, 
the reaction is reversible, for if instead of steam over hot iron, hydrogen 
be passed over hot iron oxide, iron and water are the products. The reaction 
is, therefore, correctly written thus: Fe 304 + 4 H 3 = 3Fe+4H 2 0, or 3Fe-f- 
4H 2 0 = Fe 304 + 4 H 2 . Many reversible reactions, under conditions which 
do not permit the products to escape from the field of action, do not pro- 
• ceed to completion, but reach a balanced condition after a time and seem 
to stop, though as a matter of fact they are progressing in one direction as 
rapidly as in the other, hence are described as being in dynamic equilibrium. 
In practical chemical work it is usually desirable to have reactions go to 
an end. As an aid in writing reactions the following laws may be found of 
value: 

A. The reaction of two or more substances will go to an end, that is, 
will be complete, provided, 

1. One of the products is volatile at the temperature of the reaction. 

2. One of the products is insoluble in the solvent in which the reaction 

takes place. 

3. One of the products is a non-electrolyte, that is, does not ionize in 

the solvent. 

B. The speed of a chemical action in a given direction may be increased 
by effecting a greater concentration of one of the reacting substances. 
This is a simple, non-mathematical statement of the law of mass action. 

C. Chemical reactions always tend to proceed in the direction that 
will liberate the most heat, and without the addition of heat from an external 
source those substances that have the greatest heats of formation will 
tend to form. 




18 


CHEMICAL NOMENCLATURE 


SECTION VII. 

CHEMICAL NOMENCLATURE. 

General Principle: A brief description of the nomenclature of 
chemical compounds will be found of great assistance to those not familiar 
with the subject. The names of the elements first discovered, and, there¬ 
fore, unfortunately, the more common ones, are not based on any principle; 
but of the more recently discovered elements the metals have received 
names ending in urn orium, and the metalloids, in n or ne. In the naming 
of compounds, however, the old names have been discarded and new ones 
substituted. The system employed in assigning these new names is this: 
The name of a compound should show the elements of which it is 
composed, and as far as possible their relative proportions. 

Terminology of Binary Compounds: The simplest compounds are 
those composed of only two elements. The names of all such compounds 
are made up of the name of the basic element, if one is present, succeeded 
by the name of the acid element, which ends in ide: examples; ferrous (iron) 
sulphide, FeS; sodium chloride, NaCl; calcium oxide, CaO. 

In such cases as iron and sulphur where the same two elements combine 
to form more than one compound, the compounds, when two in number, are 
distinguished by changing the ending of the metallic part of the name from 
ous to ic; thus, ferrous sulphide, FeS; ferric sulphide, Fe 2 S 3 ; stannous, 
chloride, S 11 CI 2 ; stannic chloride, S 11 CI 4 . Often, the prefixes mono-, di-, tri-, 
tetra-, pent-, per are used, especially if the name will not permit the ending 
ous and ic, or if more than two compounds are formed by the same two 
elements. Carbon dioxide, CO 2 ; nitrous oxide, or nitrogen monoxide, N 2 O; 
nitric oxide or nitrogen dioxide, N 2 O 2 ; (NO); nitrogen trioxide, N 2 O 3 ; 
nitrogen tetroxide or nitrogen peroxide, No 0 4 ; nitrogen pentoxide, N 2 O 5 
are examples. 

Terminology of Ternary Compounds: The names of compounds 
that contain three elements, provided they are not derived from acids, 
may end in ide, also, in which case all three of the elements appear in the 
name, as sodium aluminum fluoride, (Na 3 AlF 6 ), bismuth oxychloride, 
(BiOCl). A few ternary compounds derived from ic acids have names 
ending in ate as potassium chlorplatinate, (K 2 PtCle). 

Terminology of Acids: Acids are composed of the acid-forming 
elements in combination with hydrogen or with hydrogen and 0 x 3 ^gen. 
The name of a given acid is derived from the name of the acid forming 
element. The best known acid of an element has the ending ic. Example, 
chloric acid, HC10 3 . Then the acid the molecule of which contains one 
less atom of oxygen has the ending ous. Example, chlorous acid, HC10 2 . 
If the element also forms an acid containing one more atom of oxygen in 
its molecule than the ic acid, it is designated by the prefix per. Example, 




CHEMICAL CALCULATIONS 


19 


perchloric acid, HCIO4. Acids, like sulphuric (H 2 S 0 4 ) and ortho phos¬ 
phoric (H3PO4), which contain more than one replacable hydrogen atom 
are called, as a class, polybasic acids; and, in individual cases, the different 
acids are referred to as di basic, tri basic, etc., because such acids may be 
neutralized by more than one base at once. For example, potassium and 
sodium may replace the two hydrogens in H 2 SO 4 to form sodium potassium 
sulphate, NaKSC> 4 . In all such double salts both the base forming 
elements must appear in the name of the salt. 

Terminology of Bases: The base forming elements form compounds 
with hydrogen and oxygen in which these two elements appear as a radical, 
OH, called hydroxyl. Hence, these compounds are called hydroxides in 
wet chemistry. Thus, sodium hydroxide, Na OH, and calcium hydroxide 
Ca (OH )2 are examples. In dry chemistry the hydrogen and part of the 
oxygen are driven off, leaving the oxides which still act as acids and bases. 

Terminology of Salts: Salts take their names from those of the base 
forming elements and the acids of which they are composed, changing the 
endings of the acids. Salts of acids that end in ic change this ending to 
ate, and those that end in ous, to ite. Thus, sodium chlorate NaClOs, 
derived from chloric acid, sodium perchlorate NaC 104 , from perchloric 
acid, and sodium chlorite, NaC10 2 , from chlorous acid, are examples. 
Other systems of nomenclature are in use, but the ones just noted cover 
the largest field. 


SECTION VIII. 

CHEMICAL CALCULATIONS. 

Kinds of Problems: Chemical calculations constitute a very im¬ 
portant branch of study in the training of the metallurgist. They are 
of three general classes; namely, those involving weight, those involving 
the volumes of gases, and those involving both weight and volume. Further 
subdivisions of these classes may be made, the principles of which are best 
taught from specific examples, as follows: 

PROBLEMS INVOLVING WEIGHT ONLY. 

Calculation of the Molecular Weight from the Formula: Problem: 
The formula of copper sulphate is CuS0 4 . Find its molecular weight. 
Solution: From the table of atomic weights and the formula, we find 
Atomic weight of copper =63.57 Atomic No. of Combining 

“ “ “ sulphur=32.06 Weights Atoms Weights 

u “» u u oxygen =16 63.57 x 1 = 63.57 

32.06 x 1 = 32.06 
16. x 4 = 64.00 


Molecular weight of CuS0 4 = 159.63 Ans. 





20 


CHEMICAL CALCULATIONS 


Calculation of Percentage Composition of a Compound from its 
Formula: Problem: Find the percentage composition of a compound, 
the formula of which is CuS0 4 . 


Solution 


Cu 


S 


Ch 


Molecular weight=63.57+32.06+(4 x 16)=159.63. 


159.63 


63.57 


32.06 


64.00 


Percentage Composition=39.83% Copper, 20.09% Sulphur, 40.09% Oxygen. Ans. 


Calculation of Formula from the Analysis of a Compound: 

Problem: By analysis a pure compound is found to be composed of calcium 
29.41%, sulphur 23.53% and oxygen 47.06%. What is its simplest formula? 

Solution: 

Parts in a Atomic Atomic 
Element Hundred Weights Ratios 

Ca — 29.41 -4- 40.07 = .735-^-.735 

S — 23.53 = 32.06 = .735+ =.735 

O — 47.06 -4- 16. =2.941-*-.735 

Formula of compound is CaS0 4 . Ans. 

Calculation of Relative Weights from the Chemical Equation: 

Problem: Five per cent, of a certain limestone is non-volatile impurities 
and 95% is pure calcium carbonate. What will be the weight of lime 
obtained from calcining 2000 lbs. of this stone? 

Solution: 

Weight of impurities =5% of 2000= 100 lbs. 

“ “ calcium carbonate =1900 lbs. 

Reaction on calcining.CaCC >3 =CaO+C0 2 

Combining or atomic wts. . 40.00+12+(3xl6)=40.+16+12+(2xl6) 

Relative or molecular wts.. 100.00 = 56.00 + 44 

100 lbs. CaCOs gives 56 lbs. CaO 
1 “ “ “ .56 “ 

1900 “ “ “ 1064 “ “ 

1064 lbs. CaO+100 lbs. non-volatile impurities=1164 lbs. of lime. Ans. 

PROBLEMS INVOLVING VOLUME ONLY. 

Calculation of Relative Volumes of Gases: From Avogadro’s 
hypothesis, it is known that molecular weights of all gases give the same 
volume under standard conditions of 0°C and 760 mm. barometric pressure. 
Problems involving volumes of gases only are, therefore, very simple to 
solve, because the relative volumes are identical with the coefficients of 


Number of 
Atoms 
= 1 Ca 

= 1 S 

= 4 0 











CHEMICAL CALCULATIONS 


21 


the molecules, as will be evident from an inspection of the following 
examples: 

H 2 +C1 2 =2HC1 

1 vol. hydrogen+1 vol. chlorine gives 2 volumes hydrochloric acid gas 

CH 4 +202=C02+2H 2 0 

1 vol. methane+2 vol. oxygen gives 1 vol. carbon dioxide+2 vol. water 
vapor 

N 2 0 2 +02=2N0 2 

1 vol. nitric oxide + 1 vol. oxygen gives 2 volumes nitrogen peroxide. 

PROBLEMS INVOLVING BOTH WEIGHT AND VOLUME. 

Indirect Method: This method necessitates finding the relative 
weights of the gases involved, from which the volumes may be calculated 
from the specific gravity, or the weight of a unit volume. 

Problem: How many cubic feet of carbon dioxide measured under 
standard conditions would be given off by 2000 lbs. pure calcium carbonate 
during the process of calcination? 

Solution: 

Reaction CaCC >3 = CaO + C0 2 

40+12+48 40+16 12+2x16 

100 “ 56 "* 44~~ 

100 lbs. CaC0 3 give 44 lbs. C0 2 
2000 “ “ “ 880 “ C0 2 

Wt. 1 cu. ft. CO s =. 1235—lbs. 

880= .1235 = 7125—cu. ft. Ans. 

Direct Alethod: The fact that molecular weights of gases give 
constant volumes at standard conditions affords a simple direct method 
for calculating volumes from the equation. If the weights are expressed 
in grams, each gram-molecule of the gases involved represents 22.32—liters; 
if in kilograms, each kilogram-molecule stands for 22.32—cubic meters; 
and if in avoirdupois ounces, each ounce-molecule gives a volume of 22 32+ 
cubic feet. By this method the problem above would be solved as follows: 

2000 lbs.=32000 ozs. 

? cu. ft. 

CaC0 3 = CaO + C0 2 

40+12+(3x16) 40+16 
-=-b22.32 cu. ft. 

100 56 

100 ozs. CaC0 3 gives 22.32 cu. ft. 

1 “ “ “ .2232— 

32000 “ “ * 7142 —cu ft. Ans. 







22 


DESCRIPTION OF ELEMENTS 


, SECTION IX. 

A DESCRIPTION OF ELEMENTS COMMONLY MET 
WITH IN THE MANUFACTURE OF STEEL. 

Oxygen. 

Occurrence: This element is most widely distributed in nature; 
49.85% of the solid crust of the earth, 88.89% of water and 20.8% of air 
is oxygen. In air it exists in a free state. In a combined state, it exists 
in limestone, sand, marble, clay, quartz, iron ore, and manyothersubstances. 

Preparation: It is prepared by merely heating certain of its 
compounds, some of which are mercuric oxide, potassium chlorate and 
manganese dioxide; by the decomposition of water by electrolysis; and from 
the air by. purifying processes. 

Properties: Oxygen is a colorless, odorless, tasteless gas, heavier 
than air (sp. gr. =1.1056) and slightly soluble in water. At a low temper¬ 
ature and a high pressure it is converted into a liquid which boils at—181 °C. 

The phenomenon of ordinary burning or combustion is due to the 
combination of oxygen with other substances. It unites with many elements 
to form a class of compounds, the oxides. It is necessary to life. Animals 
die in an atmosphere of less than 16% oxygen. 

Compounds: Some important oxides are: carbon dioxide, CO*, 
carbon monoxide, CO, calcium oxide, CaO, magnesium oxide, MgO, ferric 
oxide, Fea 03 , and ferroso-ferric oxide, Fe 30 4 . The last two are important 
as ores of iron. 


Hydrogen. 

Occurrence: Hydrogen does not occur in nature in a free state, but 
combined with oxygen it forms water, of which it constitutes 11.11%. In 
a combined state it occurs also in the bodies of plants and animals, hence, 
in the volatile matter of coal, in petroleum, and in natural gas of which 
it constitutes almost 25%. Water is always one of the products of 
combustion when a fuel containing hydrogen is burned. 

Preparation: It can be prepared by decomposing water with sodium, 
potassium, hot iron, hot coke, or the electric current; by treating 
certain metals with certain acids; and by treating aluminum with sodium 
or potassium hydroxide. 

Properties: Hydrogen is a colorless, tasteless, odorless gas, almost 
insoluble in water. It can be converted into a liquid that boils at—252°C. 
It is the lightest substance known, being about V15 as heavy as air and 

as heavy as oxygen. Its specific gravity, air standard, is .0696. It 
is combustible and explosive. It combines with oxygen in the proportion 
of 1:8 to form water. Its great tendency to combine with oxygen makes 
it an intense reducing agent. 




DESCRIPTION OF ELEMENTS 


23 


Sulphur. 

Occurrence: This element occurs free in the neighborhood of 
volcanoes and in underground deposits, from which it may be prepared by 
purifying processes. In combined state it is found as FeS 2 , FeCuS 2 , ZnS, 
and PbS, the last three being valuable ores of copper, zinc, lead, respectively. 
It also occurs as the sulphates CaS 04 , BaS 04 and PbS 04 , and in animal 
and vegetable matter. Compounds of sulphur occur in iron ores, in 
limestone, and in coal; and these are reduced in the blast furnace, when 
a varying part of the sulphur combines with the iron, in which form it is 
very undesirable, if present in large amounts, on account of its injurious 
effects on steel and cast iron. 

Properties: Sulphur is a brittle, yellow crystalline solid which melts 
at 114.5°, forming a straw colored liquid. It is allotropic, i. e., can exist 
in different physical forms. These forms are prismatic, rhombic and 
amorphous. When heated to a sufficiently high temperature, it combines 
with oxygen to form sulphur dioxide, S0 2 , with iron to form ferrous sulphide, 
FeS, and with most of the metals, forming sulphides. The sulphur in iron 
or steel is in the forms of FeS and MnS, distributed almost uniformly 
throughout the metal while in the molten state. Upon solidifying, however, 
owing to the difference in density and fusion temperature between these 
compounds and the metal, they may, under normal conditions, segregate 
to some extent, causing some parts of the solidified mass to show a higher 
content of this impurity than the average, or of the whole in the molten 
state. With hydrogen it forms a gas, hydrogen sulphide, H 2 S,—very 
important in Chemistry. 

Uses: Sulphur is used in the manufacture of matches and black gun 
powder, also for disinfecting purposes and for vulcanizing rubber. Its 
chief use, however, is in the manufacture of sulphuric acid; and the 
amount of this acid consumed by a nation is a measure of its scientific 
advancement. 

Compounds: Besides compounds already mentioned, sulphur forms 
several acids, one of which, sulphuric acid, H^O* SO 3 (H 2 SO 4 ) is a most 
important compound. It is obtained by oxidizing sulphur dioxide, S0 2 , 
which is given off as a gas from the roasting of FeS 2 , ZnS, CuS, and from 
the burning of sulphur. 


Carbon. 

Occurrence: This element occurs free in nature in crystalline forms 
as diamonds and graphite and in the amorphous form as coal. It is the 
chief constituent of the bodies of plants and animals, of all natural fuels, 
and of nearly all prepared fuels. It occurs in combined state in limestone, 
magnesite, marble and other carbonate rocks. 

Properties: Carbon is allotropic; diamond and graphite have been 
mentioned. The common amorphoroiis forms are coal, lampblack, charcoal, 
coke, bone black and gas carbon. Its density varies with its form. 





24 


DESCRIPTION OF ELEMENTS 


Compounds and Uses: Carbon forms many compounds with 
hydrogen, called hydrocarbons, as methane CH 4 , ethylene C 2 H 4 , benzene 
CoHc, acetylene C 2 H 2 , each of which is but the first member of a series 
of related compounds. With oxygen it forms carbon dioxide, CO 2 which 
is a product of combustion and of respiration. CO '2 is also given off when 
carbonates, such as limestone, are heated. The reaction is, CaC 03 =Ca 0 
+CO 2 . Carbon monoxide is formed in combustion when the supply of 
oxygen is insufficient for the formation of CO 2 - Thus, in the blast furnace, 
a fixed amount of air is blown against an excess of hot carbon, which act 
results in this reaction: 2C+ 02 = 200 . Owfog to its t<!4 lency to combine 
with oxygen, forming CO 2 , CO is a good reducing agent. So, the CO formed 
before the tuyeres of the blast furnace reacts with the iron oxide thus: 

3 C 0 +Fe 20 3 = 3 C 0 2 +2 Fe. 

Carbon alone acts as a reducing agent in the metallurgy of iron. 

3C+Fe20 3=2 Fe+3 CO. 

Iron forms a carbide with carbon, the formula of which is FesC. In 
pig iron it is also found uncombined in the form of tiny flakes of graphite, 
hence the term graphitic carbon. Carbon has a marked effect upon iron. 
The varying properties of steel and the many uses to which it can be applied 
are due largely to the influence of this element. Carbon in steel, then, up 
to a certain limit, is not to be considered as an impurity but as an essential 
factor. 


Silicon. 

Occurrence: Next to oxygen, silicon is the most abundant element 
in nature. It is the most important constituent of the mineral part of the 
earth. Sea sand, quartz, jasper, opal and infusorial earths are almost 
pure forms of Si 02 . As silicates, it occurs in clay, mica, talc, hornblend 
and feldspar. On account of its wide distribution it forms the chief impurity 
of iron ore, as well as of nearly all natural mineral deposits. 

Compounds: As already indicated silica, Si 02 , is one of the chief 
compounds of silicon. It also forms several acids, chief of which is silicic 
acid, 2 H 20 .Si 02 (H 4 Si 04 ) which loses water when heated and forms Si 02 . 

II 4 SiO 4 =Si 0 2 + 2H 2 0. 

Thus, in whatever form silicon may occur in an ore, it is looked upon 
as Si 02 . This substance is the great acid of dry chemistry and at high 
temperatures will neutralize any base with which it comes in contact. In 
the blast furnace some of the silica (Si 02 ) contained in the charge is reduced 
to silicon. The amount so reduced varies with the working conditions of the 
the furnace, mainly the temperature. Once reduced, the silicon alloys 
with the iron and becomes a part of the metallic bath. All but traces of 
this silicon is re-oxidized and removed in the various processes of making 
steel. However, a little is beneficial to steel, so it is sometimes added in 
small amounts in the form of an iron alloy. 




DESCRIPTION OF ELEMENTS 


25 


Nitrogen. 

Occurrence and Properties: This element occurs in niter beds as 
saltpeter, KNO 3 , and Chili saltpeter, NaN0 3 , also in organic compounds 
and in coal. It is an odorless, tasteless, colorless gas that constitutes 
about 78% of the atmosphere. 

Compounds: With hydrogen it forms ammonia, NH 3 ; with oxygen a 
series of oxides, N2O, NO, N 2 O 3 , N 2 O 4 and N 2 O 5 ; and with hydrogen and 
oxygen, an important acid, H 2 ON 2 O 5 (HNO 3 ). It is a very inert element 
and has very slight effects in the manufacture of steel. Nevertheless, its 
presence in the ,ir in so large amounts makes it an important factor in 
blast furnace practice. 


Phosphorus. 

Occurrence: Phosphorus, always combined with other elements, 
occurs widely distributed in limited amounts, particularly in soils. It is, 
therefore, foimd in all iron ores. It occurs in deposits as phosphorite and 
apatite, and is an important constituent of bone. 

Properties and Compounds: While phosphorus belongs in the same 
group of elements as nitrogen, it does not much resemble it from a physical 
standpoint. It is allotropic and exists in two forms, as a pale yellow solid 
that melts readily at the low temperature of 44.1°C, and as a red form 
quite different in properties. While it is a much more active element, it 
closely resembles nitrogen chemically. It forms compoimds with hydrogen 
and oxygen,such as PH3 and P20 5 ,and an acid, H2O.P2O5 (HPO3), called 
metaphosphoric acid. It generally is found in nature as salts of 
orthophosphoric, 3H2O.P2O5 (H3PO4), and pyrophosphoric, 2H 2 0.P 2 0 5 
(H4P2O7), acids. With iron it forms a phosphide, Fe3P. It is completely 
reduced in the blast furnace, hence all the phosphorus occurring in the raw 
materials is found in the pig iron. In steel it is a very undesirable impurity, 
but fortunately it is oxidized readily, when it can be neutralized with 
lime and easily removed as part of a slag. 

Calcium and Magnesium. 

While these two elements belong to different groups, they are very 
similar so far as the manufacture of iron and steel are concerned. With 
few exceptions one may be substituted for the other without great 
inconvenience. Their oxides are the more important bases of dry chemistry. 

Occurrence and Chief Compounds : Both elements occur as insoluble 
carbonates; limestone, marble, chalk and marl are forms of calcium car¬ 
bonate, Ca0.C02 (CaCOs). Magnesite is magnesium carbonate, MgC0 3 . 
When heated, both these compounds decompose into the oxides and carbon 
dioxide, thus: 

. CaC0 3 =Ca0+C0 2 . 

MgC0 3 =Mg0+C0 2 . 

CaO represents quick lime, and MgO, magnesia. 




26 


DESCRIPTION OF ELEMENTS 


These elements also occur together as a double salt of carbonic acid, 
calcium magnesium carbonate, CaMg (C 0 s) 2 , commonly called dolomite, 
which gives calcium magnesium oxide CaO-MgO when calcined. 

CaMg (C0 3 ) 2 =Ca0-Mg0+2 C0 2 . 

Uses of Lime and Magnesia: Lime, CaO, Magnesia, MgO, and the 
double oxide, CaO MgO, are all very refractory. But on account of its 
tendency to slake in air, CaO is not used as such. Practically, MgO is 
the best basic refractory known, and calcined dolomite is the best available 
substitute. 

The oxides are reduced with difficulty, and on account of their cheapness 
constitute the principal basic fluxes. As MgO is the leading basic 
refractory, CaO is the leading basic flux. It combines with both silica and 
phosphoric acid to form readily fusible slags, which have a lower density 
than iron and consequently lie upon the surface of the metallic bath. 

Aluminum. 

Occurrence and Properties: This element in combined form is very 
widely distributed, occurring as one of the constituents of feldspar, granite, 
mica, cryolite, and all clays. It is reduced from the oxide, A1 2 0 3 , by an 
electrolytic process, in which state it is applied to many uses. It has a 
strong affinity for oxygen, violently reducing iron oxide, and on this account 
it is added to steel as a deoxidizing agent. 

Compounds: In its compounds aluminum displays decidedly basic 
properties, forming salts with all the common acids except carbonic acid. 
It forms neither a carbonate nor a sulphide. Aluminum hydroxide, 
Al(OH) 3 , however, acts like both an acid and a base. When this compound 
is heated, it loses water and forms alumina, AI 2 O 3 . It is found in varying 
amounts in all the raw materials that enter into the metallurgy of iron. 
In the blast furnace it is never reduced. Its presence, however, has a 
marked influence on the slag, affecting its fluidity and fusion temperature, 
important considerations in blast furnace practice. In its purer states 
alumina is a good refractory, but its scarcity prohibits its extensive use 
as such. 


Chromium. 

Occurrence: This element is somewhat rare. In small deposits it is 
found as chromite, Cr 2 0 3 *FeO. This substance is the best neutral refrac¬ 
tory known. In its purer states it melts at about 2175°C. 

Properties and Uses: Chromium is both acid and basic in character. 
It is very important in the manufacture of alloy, or special steels. Its 
chief effect is one of hardening, hence it is employed to increase the hardness 
of projectiles, armor plate, automobile steel, and tool steels. 





DESCRIPTION OF ELEMENTS 


27 


Manganese. 

Occurrence: This element occurs in nature as Mn0 2 , its deposits 
being somewhat limited in the United States. In very small amounts it 
is widely distributed, and is found in nearly all raw materials of iron manu¬ 
facture. About 75% of this manganese is reduced in the blast furnace, so 
it is a constituent of all pig iron. But it is readily oxidized in the purifying 
processes, and except for almost traces, that found in steel is added to it 
in the process of manufacture. Its effect in steel up to 1.0% is good, 
because it offsets the evil effects of oxygen and sulphur. Higher per¬ 
centages, 7% to 15%, are employed to produce the special steel known as 
manganese steel. 


Iron. 

Occurrence: This most important metal occurs in combined states 
and, in slight amounts, in nearly all earthy matter, as clays, soils, sands, 
etc. In deposits, it is found as the sulphide, FeS 2 , as silicates, as a con¬ 
stituent of chromite, as the carbonate, FeC0 3 , and as the oxides, Fe 2 0 3 
and Fe 3 C> 4 . The compound last named is magnetic. 

Properties: Pure iron, almost unknown, is somewhat unlike the 
ordinary commercial forms. It is grayish-white in color and relatively soft 
when compared with steel of high carbon content. It is malleable, ductile, 
and magnetic. Its specific gravity is 7.78, and its melting point in its purest 
commercial form is about 1520 °C. The presence of certain elements, notably 
carbon, silicon, phosphorus or sulphur, in the metal lowers the melting point 
rapidly. 

Compounds: Iron forms two series of compounds, the ferrous and 
the ferric. The more important ferrous compounds are FeO, Fe (OH) 2 , 
FeCl 2 , FeS0 4‘7H 2 0; corresponding ferric compounds are Fe 2 0 3 , Fe (0H) 3 , 
FeCl 3 , Fe 2 (SC> 4 ) 3 . Most of these compounds are of the highest 
commercial importance, and many will receive much fuller treatment as 
this course advances. 




28 


REFRACTORIES 


CHAPTER II. 

REFRACTORIES. 

SECTION I. 

NATURE OF REFRACTORIES. 

Importance: The problem of obtaining refractories suitable for each 
particular operation is one of supreme importance in the metallurgical arts, 
especially in the manufacture of steel. They form the chief materials of 
which all furnaces and retaining vessels are made, as well as flues and 
stacks through which hot gases are conducted. This equipment is 
expensive, and any failure in the refractories results in a great loss of 
time, equipment and product, and, too often, in loss of life as well. 

Requirements of Refractories: A refractory may be defined as any 
substance which is infusible at the highest temperature it may be required 
to withstand in service. In any particular application however, this definition 
is incomplete, because the fact that a substance is infusible does not alone 
determine its value as a refractory. An almost infusible brick, for example 
may be so fragile as to be worthless, since bricks are generally required to 
support a load in addition to resisting the effects of great heat. A perfect 
refractory would meet the following requirements at any temperature: (1) 
it would not fuse or soften; (2), it would not crumble or crack; (3), its contrac¬ 
tion and expansion would be the minimum; (4), it would not conduct heat; 
(5), it would be impermeable to gases and liquids; (6), it would resist mech¬ 
anical abrasion; (7), it would not react chemically with substances in contact 
with it. Needless to say, an absolutely perfect refractory has never been 
discovered. However, there are a number of substances which closely 
approach the first six requirements, at temperatures commonly employed 
in metallurgical work, and whether or not they will meet the seventh 
depends upon their chemical composition and the nature of the substances 
with which they are in contact. 

Classes of Refractories: Refractory substances, in common with matter 
in general, are of three classes: namely, acid, basic and neutral. Recalling 
the chemical action of acids and bases toward each other, it is at once 
apparent that a refractory of an acid character is useless in contact with 
a basic slag, and vice versa. In selecting a refractory for a specific purpose, 
the first question to be decided is what class of refractory will be required. 
Other factors affecting its life and usefulness are the amount of impurities 
it contains and the uniformity of its composition; and, in the case of brick, 




ACID REFRACTORIES 


29 


to these will be added strength, toughness, porosity, or other special 
qualities. In the manufacture of prepared refractories these factors are all 
under control, depending upon the selection of materials and the method 
of manufacture. 


SECTION II. 

ACID REFRACTORIES. 

Chemical Composition: Acid refractories owe their acid character 
only to silica, SiOs, and are of two kinds, namely, those composed mainly of 
silica and those composed of aluminum silicate, or clay. In the pure state 
silica fuses at a very high temperature, about 1830° C, a temperature much 
above that obtained in ordinary furnaces, but when heated in contact with 
basic substances it form3 silicates, some of which are easily fused. Hence, 
in refractories composed of silica the presence of impurities, alumina as well 
as the stronger bases, must be guarded against. As a refractory, silica is used 
in the natural forms of sand and cut stone and in the prepared form of 
brick. Sand (90%to 99.5% SiOs) is used to make up the bottoms of acid 
open hearth furnaces and of some types of heating furnaces. Ganister, 
a very superior material for lining converters, is a highly silicious rock. It 
has a silica content of about 98%. 

Silica Bricks are prepared from quartzite rock found in Pennsylvania, 
Wisconsin and Alabama. The rock is first crushed fine, then intimately 
mixed with a binding material which acts as a cement to hold the particles of 
silica together and to give the brick the necessary strength. For this purpose 
either clay or lime, usually in the form of milk of lime, is used, the former 
to produce quartzite brick and the latter, “silica” or ganister brick. The 
mixture, in a moist condition, is next compressed and moulded into the shape 
desired for the bricks, which are allowed to dry slowly and then are burned at 
high temperatures, about 1500° C., in large kilns. From seven to ten days 
are required to complete the burning. Silica brick expands slightly when 
heated. 

Clay is a naturally occurring earthy material which has the property of 
plasticity when wet but becomes hard when burned. The ordinary varieties 
are more or less impure silicates of aluminum, formed by the decomposition, 
or weathering, of feldspathic rock, and contain high percentages (10% to 15%) 
of combined water. They may be residual or sedimentary. Fire clays 
are of two varieties, known as plastic and flint clays; the latter is very 
hard, even when ground, but very refractory. The most refractory clays 
are associated with the coal measures of Pennsylvania. 

The impurities in clays are alkalies, due to undecomposed feldspar; 
sand; gravel; iron oxide, silicate or sulphide; calcium and magnesium 
silicates or carbonates; titania; and organic matter. Of these impurities, 




30 


BASIC REFRACTORIES 


the basic oxides are the most harmful, as they lower the fusion point 
decidedly. This is due to the fact that aluminum silicate combines with 
bases, forming double silicates. 

The process of making fire clay brick is similar to that for silica 
brick. The clay, in a finely crushed condition, is moistened with a definite 
amount of water and thoroughly mixed. When flint clay is being used, 
some plastic clay is used as a binder. Upon being dried, clay begins to 
shrink and continues to do so during the burning, when the combined water 
is driven off and the brick becomes hard. Thus, a brick, 9 inches in 
length after being burned, may measure from 9^2 to 9 z /i inches when 
moulded, depending on the mixture used. Calcined, or burnt, clay is 
employed in the mixtures to control the shrinkage. Once burned, the brick 
ceases to shrink and permanently loses the property of plasticity, which 
latter fact would indicate that the plasticity is due to combined water. 
The refractory properties of a brick depend upon the nature and amount 
of impurities and the ratio of silica to alumina. Besides its use as brick, 
clay is important as a refractory mortar to be used in laying bricks in 
furnaces and ladles, and as plaster where seamless linings are required. 


SECTION III. 

BASIC REFRACTORIES. 

Magnesia, with a melting point of 2165°C is, for practical purposes, 
the most satisfactory basic refractory. It is prepared by calcining the 
mineral magnesite, a natural carbonate of magnesium. Large deposits are 
somewhat rare. In this country very pure deposits had long been known 
to exist in the states of California and Washington, but up to the outbreak 
of the World War the entire supply was obtained from Austria and Hungary. 
Now, however, the demand is supplied almost wholly from the State of 
Washington. For this reason it is an expensive material, which fact accounts 
for its not being used except where a basic substance of the highest 
refractoriness is required. It makes an ideal brick for the construction of 
basic furnaces, and is used for the inner courses of bottoms and walls to 
slightly above the slag line. In a coarsely crushed form, described as pea 
size, it is very desirable material for making up bottoms in basic furnaces, 
as, mixed with a small percentage of basic cinder, it is readily fritted, forming 
a solid mass that resists chemical and mechanical action of the charge and the 
buoyant force of the bath. 

Lime is even more refractory than magnesia, resisting the intense heat 
of the oxyhydrogen flame, but on account of its slaking properties it is of 
little practical value as a refractory. Mixed with magnesia it gives satis¬ 
factory results. 




NEUTRAL REFRACTORIES 


31 


Dolomite, fortunately, furnishes such a mixture and occurs in this 
country in abundant quantities. Upon calcining the mineral, a mixture of 
lime and magnesia in the best proportions is obtained. It cannot be fritted 
on a bottom as well as magnesite, and the lime content fastens upon it a 
tendency to slake. In the steel industry it is used chiefly for making up 
the banks of basic open hearth furnaces. 

Bauxite is a natural form of the sesquioxide of aluminum, mixed with', 
varying amounts of earthy matter and the corresponding oxide of iron. 
It usually contains one per cent, or more of titania, T 1 O 2 . It is but feebly 
basic and, when free from silica, is highly refractory. In pure form alumina 
melts at 2010°C., but the fusion temperature of the natural bauxite will 
seldom exceed 1820°C. Recent trials indicate that it may prove to be an ex¬ 
cellent lining material, but its scarcity precludes its general use. 

SECTION IV. 

NEUTRAL REFRACTORIES. 

The Ideal Furnace Lining is a neutral material, a substance that will 
permit of changing from acid to basic, or basic to acid, processes on the same 
lining. Two such substances are well known, but unfortunately the con¬ 
ditions of natural deposits will not permit of their use except in restricted 
quantities. These, are graphite and chromite. 

Graphite: This substance is a natural product, though it can be 
prepared artifically in small quantities. It occurs mixed with calcareous or 
silicious rocks in Ceylon, Siberia, Austria, England, Brazil and New York. 
It requires expensive purification. It is infusible even at the temperature of 
the electric arc, but burns rapidly at that temperature, forming CO or CO 2 - 
At the temperature of the open hearth it would be very slowly consumed. 
It is used in making special brick, crucibles, etc. Clay may be used as a 
binding material. 

Chromite most nearly approaches the ideal refractory. Experience 
proves it to give equally satisfactory results in either an acid or a basic 
process. Its fusion point, about 2180°C., is far above the highest working 
temperature of the open hearth or blast furnace. It is difficult to set or 
sinter. In a finely ground condition and mixed with the proper proportion 
of slag also finely ground, it is used regularly in the open hearth to daub 
ports and jambs and patch walls near the slag line. In the form of brick it 
is used as dividing courses to separate acid from basic bricks, and in the 
bottoms of soaking pits, because it is impervious to pit cinder. The binding 
material for chromite brick is lime, or clay and lime. 

Protection for Refractories: The fusion temperature of the materials 
discussed is amply high to withstand the temperatures of carbon heated 




32 


REFRACTORIES 


furnaces, if resistance to heat were the only requirement. But the 
refractory must possess strength, resistance to abrasion and corrosion, etc., 
and as these properties decrease rapidly with increase of temperature, it 
is desirable, in some cases necessary, to protect them as much as possible 
from the heat. This end is accomplished by backing the brick work with 
hollow metal forms through which water is kept constantly flowing. These 
forms are made of cast iron, steel, copper, or bronze, depending upon their 
use and position in the furnace, and may be in the shape of coiled pipes, 
hollow boxes, or sprayed jackets. As this course progresses, these devices 
will be frequently met with and their value demonstrated. 

For purposes of comparison typical analyses of the various refractories 
will be found in the following table: 


Table 3. Chemical Analyses of Refractories. 


NAME PERCENT OF 



Silica 

Iron 

Oxides 

Al um- 

Lime 

Mag- 

Soda 

Potash 

Water 

Ti- 

Chro- 

Mang- 

I 

Car- 





ina 


nesia 




tania 

mic 

anese 

bon 












Oxide 

Oxide 



Si0 2 

Fe 2 0 3 

FeO 

AI 2 O 3 

CaO 

MgO 

Na 2 0 

k 2 o 

h 2 o 

Ti0 2 

Cr 2 0 3 

MnO 

C 

Ganister 

98.20 

.30 


.90 

.15 

.10 








Low Grade 














Silica Sand. . 

91.60 

3.48 


3.68 

.10 

.05 

Trace 

Trace 






High Grade 













Silica Sand. . 

99.25 

.31 


.20 

Trace 

Trace 

• • < • . 



• • • • • 




Silica Brick .. . 

96.42 

.50 


.75 

2.01 

.08 




.06 




Low Grade 














Fire Clay.... 

60.50 

2.35 

.40 

24.95 

.25 

.05 

.15 


10.00 

1.40 




High Grade 














Fire Clay.... 

50.35 

.75 


33.65 

.10 

.05 

.10 

.40 

13.75 

.80 




Low Grade Fire 














Clay Brick... 

61.72 

6.43 


28.70 

.46 

1.04 

.05 

.05 


1.60 




High Grade Fire 














Clay Brick... 

53.52 

2.00 


41.00 

.30 

.30 

.90 

.20 


1.60 




Calcined 













Magnesite.. . 

3.96 

5.81 


1.95 

.40 

87.45 








Calcined 














Dolomite.... 

1.66 

.94 


1.24 

55.01 

38.26 

1 • • • • 







Bauxite. 

4.10 

3.20 


60.80 

.04 

.04 

.10 


30 08 

1 62 




Bauxite Brick.. 

8.82 

6.30 


78.01 

.98 

4.41 



1.16 




Chromite. 

9.36 


13.50 

10.60 

Trace 

21.06 





43.97 

.80 


Artificial 












(Coke—tar) 














Graphite.... 

5.95 


2.15 

3.04 

.43 

.20 







88.20 

Natural 













Graphite 














Brick. 

13.04 


.44 

6.12 

. 

. 

. 

.43' 1.95 
i 

. 

...... 

. 

77.80 










































































TESTING REFRACTORIES 


33 


SECTION V. 

TESTING REFRACTORIES. 

Trial Tests and Laboratory Tests: The best test fora refractory is 
a trial test in which the material is placed in actual service under the most 
trying conditions it will be expected to stand up under. As such tests can 
seldom be made on material for new work and as there may be considerable 
variation in raw materials and in methods of manufacture, laboratory tests 
are necessary. Such tests are not always conclusive, owing to the difficulty 
of obtaining laboratory conditions identical to those in actual practice. 
They are, however, very useful for the purpose of comparisons, and, if the 
conditions of the tests are sufficiently severe, the more serious defects will 
be revealed. These tests are chemical and physical. From the chemical 
analysis the composition of the material is determined and its quality is 
judged. As the method of manufacture and the care with which it is carried 
out affect the properties of the refractory, the chemical test should be, 
and usually is, supplemented by physical tests. Chief among these tests 
are the fusion or softening point, crushing strength, expansion and con¬ 
traction, slagging, porosity, density, resistance to compression, impact, 
abrasion and spalling tests. Each of these tests may be made in a compara¬ 
tively simple manner, but care and judgment are required to see that the 
conditions of the tests conform closely with those to which the brick are 
to be subjected in actual service. On this account some of the tests 
usually employed will not be applicable to the iron and steel industry, 
while others must be modified to conform to its conditions. The tests 
here described are those particularly suited to this industry. 1 

The fusion temperature, in ordinary practice, is usually determined 
by means of Seger cones. These are small triangular pyramids, 6 cm. 
high, with a base of 2 cm. They are composed of aluminum silicates. Cone 
number 28 contains ten parts silica to one part alumina and corresponds 
to a temperature of 1630° C. The fusion temperatures of succeeding cones 
up to number 40, which corresponds to a temperature of 1920 °C, are increased 
by decreasing the proportion of silica to alumina. For lower temperatures 
varying amounts of alkali or lime are added. By this means the melting point 
is so controlled, that a series of cones may be prepared with melting points 
between the limits of 500° and 1900° . Upon being gradually heated to a 
sufficiently high temperature, these cones will soften and slowly bend until 
their tops touch the floor, which point is taken as their fusion point. In 
making a test, a pyramid of the material to be tested, having the same shape 
and dimensions as the standards, is placed in a furnace with two or more 
standards having melting points estimated to be near that of the material 
to be tested. As the temperature of the furnace is raised, the standard cone 
that melts at the same time as the test will register the temperature of the fur- 

i.See Practical Methods for Testing Refractory Fire Brick by C. E. Nesbitt and 
M. L. Bell. Proceedings of the American Society for Testing Materials, vol. 
XVII, 1916. 






/ 

34 TESTING REFRACTORIES 


nace and the fusion point of the test. The softening temperature is considered 
to be that at which the specimen bends, sags or puffs out of shape. Instead 
of the standard cone, the more accurate pyrometer is coming into use for 
making this test. 

Resistance to Compression: The ability of brick to withstand 
pressure at a high temperature is a very important property. This test 
is made on a modified form of Brinell ball testing machine. The ball is 
made of steel and is 234 inches in diameter. In making this test, the brick 
is uniformly and slowly heated from atmosphoric temperature to 1350° and 
held in the furnace at this temperature for three hours or longer, when it 
is removed and placed flat under the ball of the machine, and a pressure 
of 850 lbs. is immediately applied, which is gradually and uniformly increased 
at such a rate that a maximum load of 1600 lbs. is attained at the end of 
five minutes. The depth of the depression made by the ball is taken as the 
measurement of the resistance of the brick to compression. 

Expansion and Contraction : A brick must be prepared for this test 
by grinding the ends so that they will be parallel to each other and at right 
angles to the sides. Its length is then measured by means of a specially 
constructed micrometer. The brick is next heated to the temperature at 
which it is to be used, removed from the furnace and immediately measured. 
The expansion or contraction is expressed in inches per lineal foot. 

Slagging Test: By this test the impermeability of the brick to molten 
slag is determined. The brick is prepared by drilling two circular cavities, 
234 inches in diameter, each at the intersection of the diagonals of the 
rectangles formed by bisecting transversely the unbranded face of the 
brick, to such a depth that the area of the greatest cross section is 1.7 
inches. The brick is then heated as in the compression test. When the 
temperature has reached 1350°, 35 grams of a standard blast furnace slag is 
placed in one cavity and 35 grams of a standard heating furnace slag in the 
other. Both slags are pulverized to pass a 40 mesh sieve. The temperature 
of 1350° is maintained for two hours after the slag is added, at the end of 
which time the brick is removed from the furnace and, when cold, sawed 
lengthwise so as to bisect both cavities, thus exposing the part of the brick 
subject to slag penetration. The area penetrated by the slag is measured 
with a planimeter and expressed in square inches. 

Density: The density is determined from the weight of the brick in 
air and its dimensions. This method gives the apparent specific gravity. 
This test is greatly influenced by the method of manufacture, being affected 
by both the amount of water used in pugging and the pressure in moulding. 
While in manufacturing practice the amount of water added is determined 
by the plasticity of the clay, investigations have shown that the moisture 
content should be about 8% and the pressure about 1500 lbs. per square inch 
to secure the greatest density. 





TESTING REFRACTORIES 


35 


The Impact Test: This test is important in the case of brick to be 
used in blast furnace tops, where they are subject to much impact from 
lumps of ore, stone, and coke in charging. The test is greatly affected 
by temperature. A brick heated to 260°C. was found to be 20% weaker 
than one of the same brand tested at 20°C., and 40% weaker when tested 
at 540°C. In carrying out the test, the brick is first heated from 
atmospheric temperature to 260°C., the temperature being raised gradually 
through a period of one hour. The brick is then placed end up in a machine, 
by means of which a steel ball 21^ inches in diameter and weighing 2.34 
lbs. is dropped upon the longest axis of the brick from heights successively 
increasing by two inches until the brick breaks. The height in inches of the 
ball in the last test is taken as the measure of the resistance of the brick 
to impact. 

The Abrasion Test: This test aims to determine the wearing qualities 
of the brick at the temperature to which it is subjected in actual service. 
The brick is heated to the required temperature, and its end then pressed 
against a carborundum wheel for a given time and with a fixed pressure. 
The brick must be ground to uniform thickness and a preliminary cut made, 
so the wheel will cut through the entire thickness from the beginning of 
the test. The depth of the cut made on the hot brick measures the abrasion. 
It is obvious that the test will be affected by the width of the cutting wheel, 
the speed at which it revolves, also the grade and grit of the carborundum, 
all of which must be fixed and constant. 

Spalling Test: Spalling in a brick is usually produced by temperature 
changes, often accelerated by mechanical pressure. The drawbacks with this 
test are the fact that it must be made much more severe than the conditions 
of actual service and that it concerns the brick only as made, thus neglecting 
the effect of slag penetration and the resulting vitrification that often causes 
brick to spall in service. The test is usually made on several bricks. The 
bricks are dried at 100° C. for 5 hours or more, weighed, and then placed in 
the door of a furnace, heated to 1350° C., so that one end only is exposed to the 
interior heat of the furnace. The remainder of the door space, if any, is then 
filled with other brick. After heating for one hour at this temperature the 
bricks are removed, and each one is immediately plunged into two gallons 
of water at 20° C. to a depth of four inches and held there for three minutes. 
It is then withdrawn from the water, allowed to dry three minutes, and returned 
to the furnace as before. This operation is repeated until the bricks have 
been plunged ten times, when they are dried at 100° C. for five hours or more 
and again weighed. The percentage of loss in weight, which is taken as a 
measure of the spalling, is calculated from the original weight. 




3G 


IRON ORES 


CHAPTER III. 

IRON ORES. 

SECTION I. 

ORES AND THE IRON BEARING MINERALS. 

Minerals and Ores: Any homogeneous inorganic substance that 
occurs naturally in the solid state is called a mineral. A mineral, therefore, 
may be either an element or a compound. While a few elements, like 
gold and platinum, occur for the most part native, and others, like silver, 
copper, mercury, sulphur and carbon, may be found both native and com¬ 
bined, most minerals, of which some 800 varieties have been discovered 
and named, such as quartz, feldspar, hematite, hornblende, calcite, mica, 
etc., or their species, represent definite chemical compounds. Owing to the 
many forces that are constantly at work in nature and the wide distribution 
of some of the minerals, it is seldom a deposit consisting of but a single 
mineral is encountered. It is of such natural deposits that the ores are 
constituted. In general, then, an ore is defined as a mineral or a mixture 
of minerals from which one or more elements may be extracted with profit. 

The Iron Bearing Minerals: While there is a vast number of mineral 
species that contain iron, there are only a few that are of any importance 
commercially, because, in most cases, either the iron content is too low 
to justify the extraction of the metal or the mineral itself does not occur in 
sufficient abundance to make it available for use as an ore. Grouped 
according to their chemical composition, the iron bearing minerals of chief 
importance are divided into four classes; namely, the iron oxides, iron 
carbonates, iron silicates, and iron sulphides. Of these, only the first 
class may be considered as a factor in the manufacture of steel in the United 
States. These oxides go to form a large number of minerals, which have 
been grouped and named as shown in the following table: 

Table 4. Chief Iron Bearing Minerals. 

Chemical Name Mineralogical Name. 

1. Ferroso-ferric Oxide.Magnetite 

2. Anhydrous Ferric Oxide.Hematite 

3. Hydrous Ferric Oxides.Limonite and others 

4. Ferrous Carbonate.Siderite 

5. Iron Silicates.Chloropal and others 

6. Iron Sulphides.Pyrite and others 










MINERALS 


37 


Magnetite Group: The only important mineral of this group is 
magnetite, chemical formula Fe 3 0 4 , composed of iron, 72.4%, and oxygen, 
27.6%. The mineral is foimd in Arkansas, Pennsylvania, New Jersey, and 
New York. It varies in color from gray to black, has a specific gravity 
of about 5.0, and is magnetic. This last named property is taken advantage 
of in locating ore bodu s below the surface of the ground and in mechanically 
purifying ores of this group by magnetic concentration. It is often found 
closely associated with igneous rocks, when it is apt to contain appreciable 
amounts of chromium or titanium oxides which cannot be removed from it 
by magnetic concentration. The remaining magnetic ores of the United 
States are, for the most part, of a low grade and require dressing, but 
the magnetite ores of Sweden represent the purest ores in the world and 
are of a grade approaching that of the pure mineral. 

Hematite Group: The typical mineral of this group is hematite, 
which contains the equivalent of 70% metallic iron, based on the chemical 
formula Fe20 3 . It furnishes the base of the world’s most important ores. 
Being associated with rocks of various geological periods, these ores occur 
widely distributed, and in a variety of forms, which differ greatly in their 
iron content. Many of these varieties are known, from their outstanding 
characteristic, as red hematite, specular hematite, oolitic hematite, fossil 
ore, etc. 

Limonite or Brown Ore Group: The minerals of this group are all 
hydrous ferric oxides, and may be represented, as a group, by the general 
formula mFe20 3 - n H 2 O. There are five of these minerals, and they have 
been named, in the order of their progressive increase in water content, 
turgite, 2Fe 2 0 3 -H 2 0; goethite, Fe 2 0 3 TI 2 0; limonite, 2 Fe20 3 - 3 H 2 0; 
xanthosidente, Fe 2 0 3 -2 H 2 0; and limnite, Fe20 3 - 3 H 2 0. On a theoretical 
basis the iron content of this series will vary from 52.31% to 66.31%. 
These minerals are widely distributed throughout the United States. In 
southern Virginia they make up the greater part of the available ores, all 
of which are low in iron content and high in silica. 

The Carbonate Group: The representative member of this group is 
the mineral known as siderite, or iron carbonate, FeC0 3 , which contains 
43.8% of iron. Owing to the fact that carbonic acid is dibasic, a part of 
the iron required to neutralize it may be replaced by other metals, thus 
giving rise to a series of minerals, such as iron-calcium carbonate, iron- 
magnesium carbonate, etc. Some of the names commonly applied to these 
ores are spathic iron ore, kidney ore, blackband ore, etc. The ore deposits 
in which this group appears are of little commercial importance in the 
United States. In England they make up the ores of the Cleveland district. 
Usually, carbonate ores are calcined before they are charged into the blast 
furnace. 

The Mineralogical Make=up of Iron Ores: As was indicated at the 
beginning, an ore deposit at best represents but a mixture of different 





38 


IRON ORES 


minerals, only a part of which will contain the element or elements sought. 
All iron ores, then, may be looked upon as being made up of these two 
parts: One part is composed of the iron bearing minerals, which represent 
definite compounds of iron; the other part includes all the other substances 
mixed with these compounds, and is known as the gangue of the ore. 
Evidently, the richness of the ore, by which term is meant the proportion 
by weight of iron to all other elements in the ore, depends on the composition 
of the iron bearing minerals it contains and upon the amount of gangue 
associated with them. In working up the ores, their physical condition 
must also be taken into consideration. In this respect, they are subject 
to the widest variation, ranging from soft clay-like or earthy matter to 
hard compact masses. Both extremes tend to give trouble in the blast 
furnace. Thus, the soft fine ores are so apt to choke up a furnace, not 
designed to use them, that they were once considered practically worthless. 
The successful smelting of these ores represents one of the great achieve¬ 
ments of American furnacemen. One objection to very fine ores, and one 
that has not yet been overcome, is that they give rise to large amounts 
of flue dust, which interferes seriously with the economical utilization of 
the furnace gases. On the other hand, the very hard and dense ores, which 
enter the furnace in the form of comparatively large lumps, are difficult 
to reduce and require an excessive amount of fuel. 


SECTION II. 

VALUATION OF ORES. 

Factors in the Valuation of Ores: Omitting relative property 
valuations, prices of competitive ores, costs of transportation, and other 
considerations of a purely business nature, the chief factors that determine 
the value of an ore are its richness, its chemical composition and its access¬ 
ibility. The richness of the ore will, of course, be made the basis for the 
valuation. For this purpose a unit system is employed, a unit of iron 
corresponding to one per cent. But the prices of ores do not rise and fall 
parallel with the number of units of iron they contain, because the gangue 
to be disposed of must also be considered. For example, suppose two 
hematite ores containing 63% and 42% iron are being considered. In the 
first, 90% of the ore is pure mineral, leaving only 10% as gangue to be 
disposed of, but the second represents only 60% pure mineral with 40% of 
its weight as gangue to be fluxed and transported. Next to richness comes 
the consideration of the chemical composition of the ore as a whole, for 
certain impurities, when present in only relatively small amounts, may 
make a rich ore worthless. Without taking the time to consider all the 
possibilities in this connection, the more common impurities in ore may be 
classed as follows: 




IMPURITIES 


39 


1. T hose impurities that are never reduced in the blast furnace 

and so do not affect the composition of the iron are alumina, A1 2 0 3 ; lime, 
CaO; magnesia, MgO; and the alkalies, soda, (Na 2 0), andpotassia, (K 2 0). 
All these substances, it will be observed, are strong bases, with the exception 
of alumina which may be either an acid or a base. Therefore, the presence 
of these substances in the ore may not be objectionable, for the lime and 
the magnesia, in particular, are valuable as fluxes. Alumina, also, up to 
about 5%, may play a useful part in regulating the blast furnace. The 
alkalies for the most part are driven off with the flue dust, and with 
modern appliances they may be recovered, when present in sufficient 
amount to justify the installation of the necessary apparatus, so that they 
may form a valuable by-product. 

2. Those impurities that may be partially reduced in the furnace 
and give elements that enter the pig iron are silica, or the silicates, 
sulphates and manganese compounds. Of these, the silica, which term 
includes both the free silica and the silicates, constitutes a large 
part of the gangue of most ores, and as it requires an equal weight 
of lime or magnesia to flux it, it must be considered in fixing the value of 
an ore. Owing to the fact that the amount reduced in the blast furnace 
is subject to control to a considerable extent and that the element is readily 
removed during the process of purifying the pig iron, it is not considered 
of much importance from the standpoint of its effect on the steel produced 
from the iron. This attitude toward silica is just the opposite of that 
displaj r ed toward the sulphur compounds. All these compounds are reduced 
in the furnace to sulphides, in which form the sulphur enters either the 
metal as ferrous or manganese sulphides or the slag as calcium sulphide. 
Now, there is a limit to the quantity of sulphur a given slag can absorb, 
the highest figures given being less than 5%, and, naturally enough, the 
nearer this limit is approached, the more difficult it becomes to keep the 
sulphur out of the metal. Since even comparatively small amounts of 
this element exert an evil influence in steel, and it can be removed 
from the metal only partially and with much difficulty, the importance 
of this element in fixing the value of an ore is evident. As to the 
manganese compounds, the amount of this element that enters the iron 
varies with the manganese content of the ore and takes place to the 
extent of nearly 75% of the manganese charged. The per cent, of this 
element is, therefore, considered in its relation to the iron content. An 
ore is available for the manufacture of the ordinary grades of pig iron 
when the manganese content does not exceed 2% of the iron content; 
between 2% and 10%, calculated on the same basis, it is necessary to 
mix the ore with others containing little of this element; but if the manga¬ 
nese content is 15% to 20% of the iron content, then the ore becomes 
available for the manufacture of spiegel. 




40 


IRON ORES 


3. The impurities always reduced in the furnace are all the com¬ 
pounds of phosphorus, which element enters the pig iron only. While 
this element is easily removed from the metal by basic processes, none at 
all is eliminated by the acid processes, with the result that acid steels 
contain a higher percentage of this element than the average of the charge 
from which the steel is produced. This element, therefore, is the basis 
for the separation of all ores into the two great classes, known as Bessemer 
and basic. This division, like that for manganese, is made on the basis 
of the relation of the phosphorus content to iron content of the ore. Since 
it is desirable to produce Bessemer steel that will contain not more than 
.100% of its weight as phosphorus, a true Bessemer ore would be one 
whose phosphorus content plus the phosphorus content of the coke and 
limestone required to smelt and flux it would produce a pig iron with a 
phosphorus content not exceeding .090%. Allowing 10% for conversion 
loss, such a pig iron would give a steel containing less than .100% of its 
weight of phosphorus. Commercially, however, since commercial toler¬ 
ances usually permit the phosphorus in the steel to rise as high as .110%, 
no allowance is made for conversion, and a commercial Bessemer ore is 
one whose phosphorus content plus some arbitrary figure, usually about 
.015%, to allow for the phosphorus acquired from the flux and fuel, is 
less than one one-thousandth of its iron content. Thus, the per cent, of 
phosphorus in an ore containing 60 units of iron must be .045, or less, to 
be classed as a Bessemer ore, for 1/1000 of 60=.060 and .060—.015=.045. 
Another method for determining the grade of an ore is explained by the 
following example: 

Question- To what class does an ore containing 60% iron and .045% 
phosphorus belong? 


Solution: 

045-^-.60=.075=per cent, phosphorus in the pig iron, acquired from the ore. 

.020=Estimated per cent. phos. in pig iron, acquired from coke 
•- and stone. 

Ans. .095=per cent, phosphorus in the pig iron. Therefore, the ore is 
of Bessemer grade. 


Water or moisture is another factor to be considered in the valuation 
of ores, because it adds to the weight of ore to be handled and transported. 
The importance of this matter in fixing the value of an ore is seen at once 
when it is pointed out that many of the soft ores of the Lake Superior region 
carry as much as 12% of their weight as hygroscopic water, and a few as 
much as, or more than, 15%. This moisture content for any particular ore 
is much more nearly constant under varying weather conditions than might 
be expected; but in the case of different ores there is a wide variation, 
ranging from .40% in some of the hard red hematites to 16.80% in a few 





IMPURITIES 


41 


of the soft red ores. These points are well illustrated by the table below, 
the examples in which have been selected because they show about the 
same iron content when dry. 


TABLE 5. Analyses of Ores Illustrating Dry and Wet Basis. 


ORE 

STATE 

% Iron, Fe 

i 

% Phos, P. 

<3 

.2 ^ 

d 

2 

hi) 

3 

s 

is 

C4 

• E W 
a o 

%Lime, CaO 

% Magnesia, 

MgO 

% Sul. S. 

% Ignition 

Loss 

% Moisture, 

h 2 o 

A. 

(Marquette Range). . 

Dry. 

Natural.. 

57.36 

.137 

15.62 

.08 

1.26 

.68 

.33 

.007 

.03 


56.82 

.135 

15.47 

.08 

1.25 

.67 

.327 

.007 

.03 

.944 


(Missabe Range).... 

Dry. 

Natural.. 

57.03 

.042 

12.48 

.56 

1.69 

.21 

.32 

.010 

2.80 


B. 

52.54 

.039 

11.50 

.52 

1.56 

.19 

.29 

.009 

2.58 

7.87 


(Missabe Range).... 

Dry. 

Natural.. 

57.06 

.081 

7.33 

1.72 

1.00 

.30 

.40 

.010 

2.00 


C. 

47.47 

.067 

6.09 

1.43 

.83 

.25 

.32 

.008 

1.66 

16.80 


The marketing of the ores and all the metallurgical calculations 
involving them are based on the analyses of samples dried at 100°C. It 
will be observed that drying at this temperature may not drive off water of 
crystallization and that in the case of the brown hematites a much higher 
temperature than the drying temperature is required to drive off all the 
combined water. 

Accessibility; It is evident that the economic importance of an 
ore deposit depends to a great extent upon its size and its location, both 
geologic and geographic. Thus, an ore that is very desirable from the 
standpoint of chemical composition and physical condition, may be so 
located as to be practically inaccessible; or granting it can be made access¬ 
ible, the amount of ore in the deposit may not justify the expense of opening 
it up. On the other hand, a poor ore may be so conveniently located that 
it may be concentrated at a profit. A thorough discussion of this topic 
cannot be undertaken in the brief space allotted to this chapter. Suffice 
it to say, that the working of any ore body under modern conditions presents 
difficult engineering problems both in mining and in transportation. 
Perhaps the best way to impart some understanding of these problems 
is through a brief description of the ore mining operations of the Steel 
Corporation, itself. With the exception of the Tennessee Coal, Iron & 
Railroad Company, which obtains its ore from the Birmingham District 
in Alabama, all the constituent companies of the Corporation depend 
upon the Lake Superior district for their ore supply. 

























42 


IRON ORES 


SECTION III. 

THE BIRMINGHAM DISTRICT. 

Location and General Geology: The Birmingham District includes 
the area from which the furnaces at Birmingham, Ensley, and Bessemer 
secure their iron ores, and is co-extensive with Birmingham Valley. This 
Valley extends from the City of Birmingham in both a northeast and south¬ 
west direction for a total length of about 75 miles and a width of about 
six miles. The ore, which is a variety of red hematite, occurs in the Clinton 
formation, which consists of shale, sandstone, iron ore, and a little ferru¬ 
ginous limestone. Geological researches conducted by the government 1 
indicate that the ore was formed at the same time as the rocks with which 
it is associated. The valley lies within the area originally covered by 
this formation, which, therefore, occurs on both sides and dips away from 
it on each. But it is only in Red Mountain that the ore bed has been found 
of sufficient thickness and purity to justify its being worked on a large 
scale, and nearly all of the most productive mines are located in a section, 
about 62 miles long, of this mountain between Narrow Gap and Sparks Gap. 

Method of Mining: All of the red ore mines in the Birmingham 
district were started as open cuts along the outcrop, and the product of 
these surface mines, having been leached, were at first soft ore. At a 
few points these simple mining operations are still carried on, but, owing 
to the dip of the ore beds, all mines from which any large quantity of ore 
has been taken are now completely underground and are operated by means 
of slopes or inclines. At these greater depths the ore is very hard and 
compact. On account of the fact that the southern portion of the ridge 
is overlaid by more recent formations, the ore gradually becomes more 
and more deeply buried on passing southward, and all the deepest slopes 
are in the strip of mountains south-west of Birmingham. The deepest 
r slope at this southern extremity of the district extends downward on beds 
whose average dip is about 22°. The co-existance of the ore with 
limestone and the proximity of coal beds suitable for making coke give 
this district an advantage over other districts of the country. The ore 
contains phosphorus to the extent of about .8%, which is'much higher 
than other basic ores of the country. By employing the duplex or the 
triplex processes in refining the pig iron, a slag with a high phosphorus 
content is produced that is available as fertilizer for agricultural use. 

SECTION IV. 

THE LAKE SUPERIOR DISTRICT. 

Importance, Location and General Geology: During recent years 
the Lake Superior district has provided approximately four-fifths of the 
entire iron ore output of the United States, and there is nothing to indicate 
but that the region will, for many years to come, continue to be the nation’s 

Sec. Bulletin U. S. Geol. Survey No. 315, 1907. The Clinton or Red Ores of 
the Birmingham District, Alabama, by E. F. Burchard, also Bulletin U. S. Geol. 
Survey No. 340. Investigations relating to Iron and Manganese, by E. F. Burchard. 
A. C. Spencer, W. C. Phalen. 





IRON ORE RANGES 


43 


most important source of ore supply. This district, which surrounds Lake 
Superior, contains certain isolated areas, or ranges, where bodies of iron 
ore have been discovered. These ranges are scattered over the northern 
part of the states of Michigan, Wisconsin and Minnesota and also a part 
of the Canadian province of Ontario. Investigation has proven that these 
ore bodies occur at certain well defined geological horizons and are 
associated with certain rocks. Geologically, the Lake Superior deposits 
are much older than the Clinton ores of the Birmingham district, being 
associated with rocks of pre-Cambrian age. According to the conclusions 
of those who have made a study of the area, the iron was originally deposited 
as an integral part of certain sedimentary rocks. Following their deposi¬ 
tion and solidification, these rocks were elevated and folded, after which 
surface waters, bearing different compounds in solution, percolated through 
them, and, through chemical action and solution, concentrated the iron 
in the troughs which had been formed by the folding of the formation or 
by the intrusive dikes which had cut across the strata. Much later, 
with the retreat of the ice at the end of the glacial epoch, these ore 
bodies were left covered by varying depths of glacial drift. In the order 
in which they were opened the six chief areas, or ranges, lying within the 
borders of the United States, are Marquette, Menominee, Gogebic, 
Vermilion, Missabe, and Cuyuna. 

The Marquette Range lies near the southern shore of the lake in the 
state of Michigan, and a short distance west by south of the lake city of 
Marquette, from which it takes its name. Besides Marquette, the towns 
of Ishpeming, Negaunee, Champion, Republic and Gwinn are also included 
within the area. The formation is narrow as compared with its length 
and very irregular, but its general direction is from east to west. The 
original outcrop was very conspicuous and was responsible for the early 
discovery, in 1844, of the deposit, which, as indicated above, was the first 
of the great ranges to be worked. It was opened in 1854, and up to 1916 about 
119,292,000 long tons of ore had been taken out of it. The shipments for 
that year were 5,396,007 tons. The ore is partly hematite of the red, soft 
variety, but there are smaller amounts of magnetite and limonite and some 
hard hematite. 

The Menominee Range is also in the state of Michigan. It lies several 
miles due south of the Marquette range and is, hence, nearer Lake Michigan 
than Lake Superior. It includes the towns of Iron Mountain, Vulcan, 
Norway, Florence, Alpha, Crystal Falls and Iron River. The principal 
belt, composed mainly of hematite, extends in a direction from east to 
west. Only a part of the range is productive, but up to 1916 more than 
103,600,000 long tons of ore had been mined from it, and during that year 
6,365,363 tons were shipped. It was opened in 1872. 

The Gogebic Range lies almost due west of the Marquette range, and, 
extending as a narrow belt in a direction from a point a little north of east 




IRON ORES 






































IRON ORES 





























46 


IRON ORE RANGES 


to a point a little south of west of its center, it is located partly in Michigan 
and partly in Wisconsin. The area includes the towns of Hurley, Ironwood 
and Bessemer. The original iron formation, which dips sharply toward 
the north, rests on quartzite, and is cut by igneous dikes that extend at 
almost right angles to the original quartzite. The dike and the impervious 
strata thus combine to form troughs, in which ore bodies have been formed 
by concentration. The ores, which are mostly soft and red, represent 
partially dehydrated hematites, with subordinate amounts of hard, blue 
hematite. The range was opened in 1884, and in 1916 there had been 
produced from it more than 94,812,800 long tons of ore. The yearly ship¬ 
ments for 1916 were 8,489,685 tons. 

The Vermilion Range was opened the same year as the Gogebic 
range. It lies in northeastern Minnesota, and includes the towns of Tower, 
Soudan, and Ely. The whole district is one of complex folding, so the ore 
deposits occur in narrow belts, which are enclosed on the bottom and sides 
by original greenstones of Archean age and on top by the original iron 
formation. As the pitch or slope is very steep, the outcrops are very small. 
The ores are all hard and are composed of red and blue hematite. This 
range had contributed a little more than 39,526,800 long tons of ore by 1916. 
The shipments for that year were 1,947,200. This range and the three 
previously mentioned are known as the old ranges to distinguish them 
from the more recently discovered Missabe and Cuyuna ranges. 

The Missabe Range is one to excite the interest of every one interested 
in the manufacture of iron or steel, because from it comes the greater part 
of the ore used for the production of pig iron today. It was opened in 
1892 and up to 1916 about 406,855,200 long tons of ore had been taken from 
its mines. The shipments for the year were 42,526,612 tons. It lies in 
Minnesota, northwest of Lake Superior, and extends in an east and west 
direction approximately 100 miles. The principal towns are Biwabik, 
Eveleth, Virginia, Chisholm, Hibbing, Nashwauk, and Coleraine. The 
iron formation is the Biwabik in the Upper Huronian. It lies along the 
southern slope of a ridge that is known as the Giants, or Missabe, Range, 
and has a gentle slope toward the south. The surface is covered with 
glacial drift, and rock exposures are not common. This surface, originally 
covered with forest, gave few signs to indicate the presence of ore bodies. 
The slope of the iron formation is gentle, so most of the ore deposits are 
flat-lying and have a large horizontal area compared with the deposits on 
the other ranges. The impervious basement under the ore deposits is 
formed by layers of slate or paint rock, interbedded with the iron formation. 
The ores are mostly soft and hydrated hematites and limonite. They vary 
in texture from very fine dust to fairly coarse, hard and granular ore. 
Toward the western end of the district, layers of sand are often interbedded 
with the ore, forming the so-called ‘ ‘sandy’ ’ ores, which require concen¬ 
tration to form ore of commercial grade. The deposits are all compara¬ 
tively shallow. 



IRON ORE MINING 


47 


The Cuyuna Range, which is the last range of any importance to be 
discovered, was opened in 1911. It is located in Crow Wing County, Minne¬ 
sota, about 100 miles west of Duluth. The principal towns in the district 
are Deerwood, Crosby, and Brainerd. The range has no marked topo¬ 
graphic features, the surface being level and covered with a heavy mantle 
of sand. Since there are no surface indications to assist in the exploration 
for ore, the presence of lines of magnetic variation must be depended upon 
almost entirely. By drilling, these lines have been found to be associated 
with belts of iron-bearing formations which trend in a northeasterly and 
southwesterly direction. The formation is interfoliated with slate and 
schist, and is usually steeply tilted. At some localities igneous intrusive 
rocks occur. The ore deposits are usually lenticular in form. In certain 
restricted areas of the range, particularly in the northern part, mangani- 
ferous iron ores have been found. The deposits of these ores occur in 
irregular pockets or lenses, and contain as high as 45% manganese. Some 
of these bodies of ore are being worked for their manganese content only. 
In 1916 the yearly production had reached 1,716,218 tons, and the total 
production, 4,897,298 tons. 

SECTION V. 

MINING THE LAKE ORES . 1 

Prospecting and Exploration: Since the Lake Superior ores occur in 
pockets or distinct bodies and vary much as to character and location, 
the actual mining of the ores is preceded by much work of an exploratory 
character. This work includes prospecting and exploration. 

Prospecting is the term generally applied to the quest fot^urface 
indications of ore, or the conditions which would warrant the expectation 
of finding ore in the vicinity. It includes such quest operations as geological 
examination, dip needle work, shallow test-pitting, and trenching. The 
ore bodies of the Missabe Range are non-magnetic, and dip needle prospect¬ 
ing is therefore valueless. On the Cuyuna Range, however, magnetic 
attraction as evidenced by the dip needle has been extensively employed 
as a guide to the location of ore deposits; in other localities it has also 
found limited application. 

Drill Exploration: After the presence of an ore deposit is known or 
suspected, resort is generally had to exploration by means of diamond or 
churn drills. On the old ranges geological conditions generally make this 
manner of ascertaining the exact limits of an ore deposit impracticable; 
so, if two or three adjacent drill holes develop considerable depths of ore, 
the sinking of a shaft for underground exploration, development and mining 
is generally considered warranted. On the Missabe Range, however, the 
flat-lying and comparatively shallow characteristics of the ore formation 
warrant much more extensive drill explorations. On this range, then, an 
ore body is almost invariably followed out with the drills, and its limits 

lFor further details concerning the mining of the Lake Ores, see Minn. School of 
Mines Experiment Station Bulletin No. 1, Iron Mining in Minnesota, by Charles 
E. Von Barneveld, University of Minnesota, Minneapolis, Minn. 





48 


IRON ORES 











wHHS. i 




Fig. 4. Open Pit Mining 












IRON ORES 


49 



Fig. 4. Open Pit Mining 























50 


IRON ORE MINING 


are determined to the point where the complete plan of development can 
be worked out in advance of actual mining operations. 

Methods of Mining: Both open pit and underground methods of 
mining are employed in the mines of the Lake Superior District. On the 
old ranges, where the ore bodies often extend to great depths and usually 
lie at angles so steeply inclined to the horizontal that the surface exposures, 
or outcrops, are small, underground mining methods are employed almost 
without exception. On the Missabe Range the ore bodies are, as a rule, 
flatlying with relatively large areas of outcrop, and open pit mining is, 
therefore, general. Of course, there are many deposits on this range that, 
on account of limited operating area, excessive depth of over-burden, or for 
other reasons, must be mined by underground methods, and there are, 
therefore, a large number of underground mines also. But by far the 
greater part of the tonnage produced from the Missabe Range comes from 
open pits. 

Open Pit Mining: Before deciding whether an ore body should be 
mined by underground methods or as an open pit, a detailed operating- 
analysis is made of the proposition to determine by which method the ore 
can be mined most economically. Estimates are made determining the 
yardage of overburden, or “stripping”, that must be removed to uncover the 
ore body, the tonnage of ore which can then be mined by steamshovel, and 
the additional tonnage which can be “scrammed” or “milled” in the pit 
after the limits of steamshovel operation have been reached. Then the 
cost of the entire operation, including interest-charges on the necessarily 
large investment in stripping removal, is calculated and reduced to a final 
cost per ton of ore recoverable. If this figure is less than the probable cost 
per ton of underground mining, and if the other operating conditions are 
satisfactory, open pit operation is, of course, deemed advisable. The 
laying out of an open pit mine involves the following engineering problems: 
first, outlining the area of ore whichit will pay to strip, i. e., considering the 
two factors of depth of ore and thickness of overburden; second, planning the 
disposal of stripping whichit will be necessary to remove to uncover the ore 
body, for this material must often be hauled considerable distances from the 
pits to dump grounds; third, locating the track systems outside the pit 
for the transportation of stripping and the hauling of ore; fourth, designing 
the system of railroad tracks within the pit that will make available the 
maximum quantity of ore accessible by steamshovel, which designing 
generally involves a series of switchbacks on limiting operative grades and 
curvature; fifth, providing for drainings of the pit; and sixth, planning 
in advance for the mining of the ore that cannot be mined by steam¬ 
shovel. The general term open pit mining covers three recognized 
methods of mining, i. e., steamshovel, milling and scramming. Steam¬ 
shovel mining, of course, needs no description; it is simply the loading 
of ore directly into railroad cars by steamshovel. 




IRON ORE MINING 


51 



Fic. 5. Open Pit Mining. Steam Shovel with Four Yard Dipper Loading Stripping. 
















52 


IRON ORE MINING 


Milling is a term applied to a thoroughly well worked out system of 
open pit mining, extensively prosecuted in the early days and still applied 
under suitable conditions. It consists of the following operations: first, 
the removal of the overburden from the ore body to be mined, this being 
done by steamshovel; second, the sinking of a hoisting shaft or incline to 
the bottom of the ore and the development of a system of underground 














IRON ORE MINING 


53 


tramming drifts tributary to the shaft and underneath the ore to be 
mined, third, the putting up of a number of raises (vertical openings) 
extending from the underground drifts through the ore; fourth, “milling” 
or shoveling the ore into the raises, through which it is drawn into tram 
cars operating in haulage drifts that lead to the shaft or incline, where it is 
hoisted to the surface. The milling system of mining can well be applied to 
small ore bodies which can be successfully stripped, but where the resultant 
open pit areas are too small to permit of steamshovel operation; also, as a 
sequel to steamshovel mining in larger pits where considerable depths of 
ore remain after the limits of steamshovel work have been reached. 

Scramming is a term applied colloquially on the Missabe Range to 
the operation of recovering shallow pockets and hummocks of ore left 
unmined in and around the open pits following the period of steamshovel 
mining. It is a general term inclusive of hand wotk, scraper work, mining 
with dragline excavators, etc., and is applicable generally to the operation 
of “cleaning up” a pit after its period of real production has passed. 

Advantages of Open Pit Mining: It is very apparent that open pit 
mining, when feasible, offers decided advantages as compared with under¬ 
ground methods. Probably, the most evident of these is the possibility of 
big production; in 1916 the Hull Rust Mine alone shipped 7,665,611 tons of 
ore,—more than 10% of the total mined in the United States during that 
year, which, according to the U. S. Geological Survey, amounted to 
75,167,672 tons. Where the overburden is light in comparison with the 
depth of ore, and stripping charges are not heavy, open pit mining produces 
low cost ore. It accomplishes a great saving in labor; the output per man 
per day from the open pit mine is many times that from the average 
underground mine. Aside from the skilled operators of the steamshovels 
and locomotives, common labor only is required in open pit mining, while 
in underground work the miner is a rather high class workman, and he 
receives a relatively high wage. Owing to this latter condition, strikes 
have never been able to interfere seriously, so far, with the output of 
Missabe Range open pit mines. 

Underground Mining—Slicing: The system of underground mining 
most generally in use in the mines of the Missabe Range, and in the soft-ore 
mines of the old ranges, as well, is known as top=slicing and caving. The 
development of a mine under this method is as follows: First, a shaft is sunk 
to the bottom of the ore body, or to such depth in the ore as has been 
determined as desirable. Second, after cutting a “station,” pumproom 
and pocket at the bottom of the shaft, a main haulage drift, or system 
of haulage drifts, is driven out underneath the ore body. Third, raises are 
put up from the haulage drifts at intervals of about 50 feet along the drifts 
through the ore body to the top of the ore. Fourth, cross cuts are driven 
from the tops of the raises to the limits of the ore body or the property 
lines, the cross cuts being parallel and the same distance apart as the 




54 


IRON ORE MINING 


raises. Fifth, beginning at the ends of the cross cuts farthest from the 
raises, the ore is “sliced” out between cross cuts, trammed to the raises, 
dumped into the latter, drawn off thru chutes into cars operating on the 
main haulage level, hauled to the shaft, dumped into the shaft pocket and 
hoisted to the surface, where it is either loaded direct into railroad ore 



Fig. 7. Underground Ore Mining—Square Set Timber. 












GRADING 


55 


cars, or (if in the Winter time) stockpiled for later shipment. A “slice” 
consists of a room opened up between crosscuts, and may be one, two or 
more sets wide depending on the tendency of the overburden to crush the 
temporary timber supports. When the ore has been removed from the room 
or slice, the supporting timbers are blasted out and the overburden allowed 
to cave and fill it. Before blasting the timbers, however, boards are laid 
over the floor of the room to prevent admixture of the caved material 
with the ore below. While slicing and caving operations are proceeding 
on the top level, the cross cuts to develop the next level immediately below 
are being driven, and as soon as considerable areas of cave have been 
developed on the first level, slicing under these areas is started on the 
second level. Thus, the entire ore body is mined, slice by slice, and level 
by level. Levels are generally about eleven feet apart, floor to floor. 
Haulage of ore on main levels from chutes to shaft may be by hand, mule or 
electric motor, depending on the size of the mine. On the sub-levels the 
ore is hand-trammed in small dump cars, or for short hauls, in wheelbarrows, 
from the slices to the raises. 

Advantages of the Slicing System of Mining: The top-slicing-and" 
caving system has many advantages. It gives a high percentage of ore 
extraction. If desired, the ore from different working places can be 
separated, and two or more grades can be produced from the same mine. 
Development and mining operations are simple and safe, and can be carried 
out along well defined plans worked out in advance. While the consumption 
of mining timber is high, cheap inferior grades are used, and under ordinary 
conditions this item of cost is not excessive. In common with most other 
systems of mining, it possesses the disadvantage of a limited number of 
working places; considerable handling of the ore is also necessary. 

The depth of mine shafts on the Missabe Range rarely exceeds 350 
feet. The average is probably between 250 and 300 feet. On the old ranges, 
where the rock formations have been folded and tilted, mining operations 
extend much deeper. Here mine shafts 500 to 1500 feet deep are common, 
while in some cases mining operations are still in ore at depths well in 
excess of 2,000 feet. 

Grading the Ores: In the early days of iron ore mining, no grading 
of the ore from analysis, such as prevails today, was made, and the ore 
was known by the name of the mine that produced it. Then, the number 
of mines was small, and the ore from any one mine was fairly uniform. 
As the production increased, however, and the field of available ore was 
broadened to include deposits previously regarded as unprofitable, it 
became necessary, in order to simplify shipping, to grade ores according 
to their composition, and, further, to mix ores differing in composition to 
produce certain grades. Finally, it became quite common for one mine 
to ship several different grades, and for the ore from several mines to 
be grouped under one name. These conditions brought about a necessity 




56 


IRON ORES 


for knowing the exact composition of the various ores, and whether or not, 
in the case of mixed ore, each cargo was of the grade guaranteed. This 
grading is done by sampling the ore in the cars as fast as they are loaded 
at the mine, in lots not exceeding ten, and making a rapid but accurate 
analysis for the determining elements. From this analysis the class or 
grade of the ore is fixed, and its allotment into a certain group can be made. 
This is the work of the grader, who, from the analysis of the cars as sub¬ 
mitted to him, makes a theoretical shipment in which the contents in 
silica, iron, phosphorus and possibly manganese, the determining factors 
in the value of an ore for its particular purpose, must fall within certain 
predetermined limits. 

Transporting the Ores: The Lake ores now supply all the furnaces 
in Western New York, Western Pennsylvania, Ohio, Illinois, and Indiana, 
as well as those in the ore producing states of Michigan, Wisconsin, and 
Minnesota. In order to reach these markets, the ores must be transported 
for distances varying from 300 to more than 1000 miles, depending upon 
the locations of both the mine and the furnaces. The cost of transporting 
this ore by rail alone would be a serious handicap to some furnaces, but 
fortunately the chain of Great Lakes affords a cheap mode of transportation 
for the greater part of the long as well as the short distances. Nearly all 
the ore mined in the ranges, then, goes first by rail to a harbor on Lake 
Michigan or Lake Superior, where it is loaded on ore carrying boats that 
carry it either down Lake Michigan to Chicago or Gary or through Lake 
Huron and Lake Erie to ports further south. For most of the ore, even 
these lower lake ports are not ultimate destinations, and another haul by 
rail is required to place it at the furnaces. Now, to return to the grading 
of the ore, what was there referred to as a theoretical shipment might 
better have been called a theoretical cargo or boat load. When the cars 
containing this theoretical cargo, which may weigh from 3000 to 13,600 
tons, depending upon the size of the boat, reach the dock at the shipping 
port, they are unloaded into the dock pockets, one on top of the other, 
three to six cars to a pocket, in such order as to mix the ore as much as 
possible. The ore is then allowed to flow from these pockets into the 
hatches of the steamer, thus, again mixing the ore. Then the boat 
proceeds to her destination, where the ore is unloaded by electrical, 
or otherwise operated, grabs, which process of unloading still further 
tends to mix the ore and make it uniform. All this mixing of the ore 
is not to be thought of as merely incidental to the operations, but 
as a necessary course of procedure, for uniformity in the ore is a very 
important requirement in the successful operation of the blast furnaces. If 
the ore is unloaded at the works located on the lakes, it is sampled for 
analysis during the unloading by an elaborate system and is dumped 
upon its appropriate stock pile; if for inland works, such as Pittsburgh, 
it is placed in cars and ultimately reaches the works, where each car is 
sampled, according to printed instructions common to all the works of 




IRON ORES 


57 


the Steel Corporation. The cars are then unloaded upon a stock pile from 
which the ore can be used as needed, or directly into the furnace bins, 
if the ore is needed for immediate use. 

Mining and Grading in Winter: In winter the procedure as outlined 
above has to be changed somewhat. During a part of November, and all 
of the winter months of December, January, February and March, the ore 
cannot be transported over the lakes because of the ice. On this account, 
operations in the open pit mines of the Missabe District are suspended in 
winter; but in all the underground works, both of the old ranges and the 
Missabe, mining is continuous throughout the year, and the ore mined 
during the non-shipping season must be stock piled. As this ore is removed 
it is carefully sampled, and average samples are analyzed daily. These 
analyses, supplemented by those made in the work of exploration that is 
constantly carried on in advance of the mining, make it possible to calculate 
the average composition of each stock pile at the beginning of the shipping 
season in the spring. This stock, therefore, may be combined, if necessary, 
with the ore direct from the mines to make up cargoes of definite and known 
composition. 



58 


FUELS 


CHAPTER IV. 

FUELS. 

SECTION I. 

SOME PRE-REQUISITES TO THE STUDY OF FUELS. 

Introductory: There are five basic materials upon which the 
metallurgical arts depend; namely, ore, fuel, flux, air and water. Of 
these one is as important as the other, for all metallurgical industry would 
cease with the failure of any one. At one time all these were thought to 
be inexhaustible, but recently it has been generally recognized that the 
supply of the higher grades of ore are limited, and that the more suitable 
fuels, at the present rate of consumption, must be exhausted in a compara¬ 
tively short time. Representing the only source of energy under man’s 
absolute control, fuels are the foimdation upon which a nation’s progress 
and prosperity depends. The subject is also a very large one. Hence, in 
this chapter it is desirable to discuss briefly a few fimdamental topics of 
general interest, and more in detail, a few matters especially important in 
the iron and steel industry. 

Sensible and Specific Heat: Provided no change of state or of allo- 
tropic form is involved, the effect produced by imparting heat to a body 
is a rise in temperature of the body, and if the body is made to give up 
heat, its temperature falls. This heat, which is easily detected, is often 
spoken of as sensible heat. The quantity of heat required to raise the 
temperature of a body 1°C. is called its thermal capacity. The amount 
of heat required to raise the temperature of equal masses of different 
substances 1°C. varies greatly, and the thermal capacity of one gram of 
any substance, in other words, the number of calories required to raise 
the temperature of one gram 1°C., is called its specific heat. Specific 
heats are determined by the method of mixtures, which is based on the 
law of heat exchange. This law states that -when bodies at different 
temperatures are brought into contact, exchange of heat takes place until a 
imiform temperature for all is reached, and that the heat lost by the hotter 
bodies equals in quantity that gained by the colder ones. The specific 
heats of a few common metals follow: Iron=.109 cal. Copper=.092 cal. 
Zinc=.093 cal. Mercury=.033 cal. 




HEAT LAWS 


59 


Latent Heat and Change of State: Changes of state are governed 
by the following laws: 1 

Laws of Fusion: 

I. Every crystalline substance begins to melt at a definite temper- 
ture, which is invariable for each substance if the pressure is 
constant.” 

II. “The temperature of a body, when slowly melting, remains constant 
till the whole mass is melted.’' 

III. “Substances that expand on solidifying have their melting points 
lowered by pressure, and vice versa.” 

Laws of Evaporation: 

I. “The rate of evaporation increases with rise of temperature.” 

II. “The rate of evaporation increases with the surface of the liquid 
exposed.” 

III. “The rate of evaporation is increased by a continual change of 

air in contact with the liquid.” 

IV. “The rate of evaporation is increased by diminishing the vapor pres¬ 

sure, that is, by applying suction to the vessel inclosing the liquid” 

Laws of Ebullition: 

I. “A pure liquid has a definite boiling point, which is invariable 
for that liquid under the same conditions.” 

II. The temperature of the vapor given off by a pure liquid near its 
surface remains constant till all the liquid is vaporized if the 
pressure remains constant. 

III. “The boiling point of a liquid is raised by salts and lowered by 

gases dissolved in it.” 

IV. “The boiling point of a liquid rises with increase of pressure and 

falls with decrease of pressure.” 

It will be noted from these laws that when change of state takes place, 
there is no change in temperature of the body, notwithstanding the constant 
application or withdrawal of heat. The heat thus involved is sometimes 
spoken of as latent heat, though heat of fusion and heat of vaporization 
would appear to be the better terms to employ. The heat of fusion for water 
is about 80 calories per gram, while its heat of vaporization is 535.9 calories 
per gram under standard pressure. 

Transmission of Heat: Heat is transmitted in three ways; namely, by 
conduction, by convection and by radiation. Conduction is the transmission 
of heat through a body without visible motion of the body, as through an 
iron bar. When the heat is transmitted by mechanical motion of the 
particles of matter, through air or water currents for example, it is called 
convection. The distribution of heat through a blast furnace makes use 
of these principles. Radiation refers to the transmission of heat, independ¬ 
ently of matter, by means of waves in the ether. This is the means by 
which the heat of the sun reaches the earth. These factors are important con¬ 
siderations in the action of furnaces, stacks, ventilators and h eating plants. 

1 See High School Physics and University Physics by Henry S. Carhart and Horatio 
N. Chute, published by Allyn and Bacon, Boston and Chicago. 







60 


FUELS 


Fuels and Combustion: Any chemical reaction by which light and 
heat are evolved is called combustion. In the ordinary cases of combustion, 
one of the reacting substances is the oxygen of the air. Therefore, fuels 
are sometimes defined as substances which will burn in air and liberate 
heat with sufficient rapidity to be applied to practical purposes. The chief 
elements constituting fuels are carbon and hydrogen, though in certain 
processes silicon, phosphorus, sulphur, manganese and the metals may 
serve as fuel. In metallurgy the fuel is often required to act as a reducing 
agent, in which cases the total heat produced will be derived from two 
sources, namely, by combustion with oxygen of the air and by combination 
with oxygen of the ore. 

Fuels and Chemical Energy: Fuels represent potential energy, 
which is given off as heat by chemical action. Therefore, the relations 
of the weights of fuel, weights of air, and the amounts of heat evolved are 
fixed quantities. The following reaction furnishes a simple illustration: 

C T 0 2 =C0 2 T Heat, 

that is, 12 gm.C+32 gm.0 2 =44 gm.C0 2 +97200 cal. (Heat of formation of C0 2 ) 
orl gm.C+2.666 gm.0 2 (11.51 gm. air)=3.666 gm.COo+8100 cal. (Calorific 
power of carbon). 

The heat liberated is referred to in two ways. The chemist bases his 
calculations on the total heat evolved to form a molecular weight in grams 
of a given substance, in this case, 44 gms. C0 2 , which is called the heat 
of formation for that compound. But the metallurgist and engineer 
employ the heat evolved from a unit weight of fuel, in this case, one gram 
of carbon, and refer to it as the calorific power of the fuel. It should be 
observed that these terms take into consideration only the total amount 
of heat evolved, irrespective of the time or speed of the reaction, the 
duration of which may vary through wide Unfits. This point is important 
in the attainment of high temperatures and is connected with the second 
important factor affecting the combustion of fuels, namely, the temperature 
to which the products of combustion may be raised by the heat evolved. 
This is referred to as the calorific intensity of the fuels. Both the calorific 
power and the intensity enter into the valuation of fuels. 

Measurement of Calorific Power: As has already been noted, the two 
practical heat units are the large calorie and the B. t. u. Metallurgists 
express the calorific power in large calories per kilogram, which is numer¬ 
ically the same as small calories per gram employed by chemists, while 
engineers use B. t. u. per pound of fuel as the basis of their calculations. 
The units are readily converted from one to the other; the relation with 
respect to the quantity of heat they contain is expressed thus: 

B. t. u. per lb.: Cal. per kilo=l : 1.8 

Hence, to reduce Cal. per kilo, to B. t. u. per pound, it is only necessary 
to multiply by 1.8. The factor for changing B. t. u. per lb. to Cal. per 
kilo, is .5555. 






CALORIFIC POWER 


61 


The Calorific Power of some common elements in simple oxidation 
reactions is as follows : 1 


Table 6. Calorific Power of Some Elements. 


Element 

Reaction. 

Calorific Power in Calories per Kilo. 

H 

2 H 2 + 02 = 2 H 20 Liquid 

34500 

H 

2 H 2 + 02 = 2 H 20 Vapor 

29030 

C 

c+o 2 =co 2 

8100 

C 

2C+0 2 =2C0 

2430 

Si 

Si+ 0 2 =Si0 2 

7000 

A1 

4A1 +302=2Al203 

7270 

P 

4P+50 2 =2P 2 0 5 

5895 

S 

s+ o 2 =so 2 

2196 

Fe 

3Fe+202=Fes04 

1612 

N 

N 2 + 0 2 =2NO 

—1541 


Calculating Calorific Power: Given the heats of formation of the 
reacting substances and of the products of combustion, it is possible to 
calculate the calorific power of some fuels from their analyses. The calorific 
power of a well made coke can be estimated approximately from the fixed 
carbon, if the moisture and volatile matter are low. 

By analysis, Fixed Carbon=87.0% 

Calorific Power of Carbon=8100 Cal. per Kilo 

.87 


7047 Cal. per kIlo.=calorific power of coke 

This calculation for gases becomes more complicated, because the 
calorific power is usually expressed in Calories per cubic meter or B. t. u. 
per cu. ft. This fact requires a conversion from weight to volume, since 
the calorific powers in the table are based on weight. This conversion, 
however, is a simple matter, since a gram molecular weight of any gas has 
a volume of 22.32 liters under standard conditions. To find the heat evolved 
from a gas in calories per liter, it is only necessary to divide the heat of 
formation by 22.32. In the case of a blast furnace gas composed of CH 4 , 
. 2 %; CO, 25%; H 2 , 3%; C0 2 , 12%; N 2 , 59.8%; the calorific power may be 
found as follows: The reactions that may occur in complete combustion 
are 

Reaction (1) CH 4 + 202 = 2 H 20 +C 02 

Heats of formation, 21700 cal.+0=2x58060 cal. +97200 cal. 

Reaction (2) 2 C 0 + 02=2 CO 2 

Heats of formation, 2x29160 cal.+0=2x97200 cal. 

Reaction (3) 2 H 2 + 02 = 2 H 20 
Heats of formation, 2x58060 cal. 

1 See. Metallurgical Calculations by Joseph W. Richards, One Volume Edition 
published by McGraw-Hill Book Company, New York. 








62 


FUELS 


From reaction (1) the total heat available from CH 4 = 

2x58060+97200 21700 = _^^ _|_ pa | or j ea p er liter. 

22.32 

From (2) available heat from CO= 

?Zr22lIr?i??=3048+calories per liter. 

22.32 

From (3) available heat from H 2 = 

116310 _2605,+calories per liter. 

2x22.32 

Total heat of gas available is, 
for CH 4 .2% of 8585= 17.17 

CO 25% of 3048=762.00 
H 2 3% of 2605= 78.16 

857.33 calories per liter at 0°C. and 760 m. m. 
pressure= (857.33 x .11236)=96.33—B. t. u. per cu. ft. 

Practical Tests: All calculated results, however, are usually higher 
than can be obtained in actual practice. Furthermore, with complex fuels, 
like coals, the composition of which can only be guessed at, it is impossible 
to make accurate calculations from the analysis, because no account is 
taken of the heat required to decompose the fuel and gasify the products. 
Many fuel chemists, however, have evolved formulas by which they are 
able to determine very closely from the analysis the calorific value of a 
coal as obtained by laboratory experiment. Nevertheless, experimental 
methods are relied upon almost wholly to determine the heating power 
of fuels. These tests may be practical, in which large quantities of the 
fuel are consumed under conditions approximating closely those of the 
process for which the fuel is to be used; or they may be laboratory tests, 
in which small quantities of fuel are burned, and the heat evolved is 
measured. Practical tests may be made in specially constructed apparatus 
or under boilers in actual service. These specially constructed apparatus 
are in the form of large heaters through which water circulates and in which 
the fuel may be completely consumed. From the amount of fuel consumed, 
the weight of water heated, the rise in temperature of the water, the 
difference in temperature between the in-going air and the products of 
combustion, the calorific power may be accurately determined. 

Laboratory Tests: For determining the maximum amount of heat a 
given fuel is capable of generating, laboratory tests are more exact than 
practical tests. Such tests are carried out in specially designed apparatus 
called calorimeters. There are several makes of these instruments, but 









CONSERVATION OF HEAT. 


63 


the fundamental principles of all are the same. The process consists in 
completely oxidizing the fuel in a space enclosed by a metal jacket (the 
bomb) so submerged that the heat evolved is absorbed by a weighed 
portion of water contained in a perfectly insulated vessel. From the rise 
in temperature of the water, the heat liberated by one gram of the fuel is 
calculated. The best types of calorimeters are those called oxygen bomb 
calorimeters, in which the fuel is burned in the presence of compressed 
oxygen. 


Calorific Intensity: The calorific intensity is more precisely defined 
as the degree of heat evolved by a given weight of fuel in perfect combustion 
in air at 0°C. and 760 m. m. pressure. The theoretical maximum temper¬ 
ature depends on the calorific power, and the density and specific heats of the 
products of combustion, and is inversely proportional to the time required 
in producing it. In practice the temperature is also affected by the initial 
temperature of the fuel and air, the amount of air used, amount of water 
in fuel and air, and by radiation, conduction and convection of materials 
of the furnace. As the attainment of high temperatures is necessary to 
many metallurgical processes, all these factors are important, and special 
devices have been invented to prevent waste, preheat air and gas, and 
eliminate moisture. 

Methods of Conserving Heat: Owing to the high temperature at 
which the products of combustion escape from furnaces and the large volume 
of air necessary for the combustion of the great quantities of fuel used, 
much of the heat generated in the furnace is carried away by the outgoing 
gases and wasted, unless special methods are employed to recover this waste. 
This can be done in several ways. The hot gases may be passed through 
boilers and made to generate steam, conducted into other furnaces requiring 
lower temperatures, or used to preheat the air and fuel and thus increase 
the intensity of the heat in the furnace. Since high temperatures are 
required in most metallurgical processes, the third option is generally 
selected. The methods by which this preheating is accomplished depends 
upon two principles, called the regenerative and the recuperative. In 
the regenerative method the hot gases from the furnace are conducted 
through expanded portions of the horizontal flues, almost filled with open 
brick work, called the “checkers” from the manner of laying the bricks. 
When the checkers have absorbed heat sufficient to raise their temperature 
to nearly that of the gases, their connection with the stack is closed, and 
the air, or air and fuel, if the latter can be preheated, is made to pass through 
the checkers on its way into the furnace, thus taking on the stored up heat in 
the checkers. With two such sets of checkers to a furnace this process is 
made practically continuous by reversing the direction of the gases at short 
intervals. In the recuperative method the checkers are replaced by a 




64 


FUELS 


system of pipes through which the out-going gases must pass. The in-going 
air, being at the same time drawn in through the space around the pipes, 
is heated in proportion as the waste gas is cooled. 

Pyrometers: The measurement of high temperatures requires special 
instruments called pyrometers, many of which are made self recording so as to 
measure continuously the temperature of a furnace through long periods of 
time. There are many tj^pes of these instruments, and only the principles 
upon which some of the more important types are based will be briefly 
described. 

Specific Heat, or Water, Pyrometer: This is an old type of instrument, 
and one that is still extensively used. The operation of the instrument is 
carried out as follows: A weighed amount of metal of known specific heat 
is placed in a furnace, and when it has attained the temperature of the 
furnace, it is withdrawn and quickly dropped into an insulated vessel, con¬ 
taining a definite amount of water and provided with a thermometer for 
reading the temperature of the water. The rise in temperature of the 
water is proportional to the weight of the ball, its specific heat, and the 
temperature of the furnace. The first two factors being known, the 
temperature of the furnace can be readily calculated. 

Electric Resistance Pyrometers: Instruments of this type depend on 
the fact that the electrical resistance of metals increases with rise in their 
temperatures. In practice the metal will be platinum in the form of wire, 
which will be inserted in one arm of a wheatstone bridge for measuring 
resistance. A battery and a galvanometer for detecting difference in 
potential, both being attached to the bridge, completes the apparatus. In 
operating the instrument, the slide on the bridge is adjusted so that the 
resistance of the two arms of the bridge are the same and the galvanometer 
reading is zero. The “bulb” of platinum wire is now inserted in the furnace, 
when, the resistance of the platinum wire being increased by the rise in 
temperature, it is necessary to insert resistance in the other arm of the 
bridge to keep the galvanometer reading at zero. The amount of the 
resistance inserted measures the increase in resistance of the wire, which 
can be interpreted in degrees of temperature. 

Thermo=Electric Pyrometers: These instruments are both con¬ 
venient and accurate, being very simple in construction. They depend 
upon the fact that if two metals are in contact at a given point, any change 
in temperature at that point causes an electric current, the intensity of 
which is proportional to the change in temperature, to flow around a circuit 
connecting their free ends. This current can be measured by inserting a 
millevolt meter in the circuit. In practice the metals employed for high 
temperatures are platinum in conjunction with an alloy of platinum and 10% 




PYROMETERS 


65 


rhodium or iridium in the form of wires, which are insulated from each other 
by means of hollow tubes of refractory materials. For low temperatures the 
baser metals may be used, such as iron and nickel-copper alloys. 



Fig. 8. Diagram of Wiring for Thermo-Electric Pyrometer* 


Radiation Pyrometers are based on the law of heat radiation which 
is briefly stated thus: The energy emitted by a highly heated black body 
is proportional to the fourth power of its absolute temperature. Such 
instruments consist of a millevoltmeter and a telescope which contains a 
concave mirror reflector and a delicate thermo electric couple. By pointing 
the telescope, from a certain distance, toward a highly heated surface, a 
portion of the radiant heat is made to fall upon the mirror, which con¬ 
centrates the rays upon the couple, causing it to generate a current that 
can be measured by the millevolt meter. 

Optical Pyrometers depend upon the relation of the intensity of light 
emitted by an incandescent body and its temperature. In them the 
intensity of the light from the hot body is compared with that of an incan¬ 
descent lamp. The simplest form consists of a telescope containing the 
lamp and a battery to supply the current. In making a determination, 
the telescope is pointed at the heated body, and the current is adjusted 
so that the intensity of light from the filament of the lamp matches that 
from the body. From the adjustment necessary the temperature of the 
body is determined. In improved forms of this instrument, a circular plate 
of colored glass is inserted in the telescope between the lamp and the eye 
in such a manner that the light from the lamp falls on one-half of this plate 
and light from the body falls on the other. The two lights are matched 
by varying the intensity of the light from the body with a diaphragm. A 
second improvement is made by providing a special rotating prism by means 
of which the lights from both the body and the lamp are varied in intensity. 
The amount and direction of rotation necessary to match the lights measures 
the temperature. 

All modern pyrometers are constructed with graduated scales to read 
in degrees, so that no calculations for converting the various relations into 
temperatures are required. 







6(3 


FUELS 


SECTION II. 

CLASSIFICATION OF FUELS. 


Of the many ways of classifying fuels, that shown below in Table 7 
is a very logical and simple one and most convenient for the purposes of 
this chapter. It requires no explanation. 


Table 7. Classification of Fuels. 

Hard. 


Carbon- 

Hydrogen 

Fuels 


Solid 


Natural 


Wood< 


Soft. 


n , /New. 

Peat (old. 


Lignite 


/ New. 
\01d. 


Liquid < 


n . {Bituminous. 
CoaL (Non-coking. 

Anthracite. 


[ Briquettes. 

Prepared \ Pulverized Coal. | Charcoal. 

Carbonized Fuel \ ~ , f Beehive. 

l Coke (By- P roduct. 

N atural—Petroleum. 

Distilled Oils. 


Prepared^ 


Coal Tar. 


Gaseous 


Natural—Natural Gas. 

Producer Gas. 

Blast Furnace Gas. 
Prepared-j Coke Oven Gas. 
Coal Gas. 

Blue Gas. 


f 


Iron. 

Manganese. 
Carbon. 
Silicon. 
Phosphorus. 

Sulphur Works<[ Poa f ing - 


Incidental j Bessemer Converter < 
Fuels 


’\ Smelting. 


















LIQUID FUELS 


67 


Plan of Study: In discussing the different fuels it does not seem 
desirable to follow the order of the outline above. Some, like blast furnace 
and coke oven gases, are best taken up in connection with the processes 
that produce them, while others, like the distilled oils, are of so little 
importance from a metallurgical standpoint that they cannot be more than 
mentioned here. Concerning the others, which play more or less prominent 
parts in metallurgical processes, it is the intention to dispose very briefly 
of the less important first, so that the attention may be concentrated upon 
the more important ones, which will be taken up at the last. 


SECTION III. 

INCIDENTAL AND LIQUID FUELS. 

Incidental Fuels: Under this heading is included all substances 
which incidentally act as fuels in certain processes. In the acid Bessemer 
converter, for example, the oxidation of the impurities, silicon, manganese 
and carbon, to which is added phosphorus and sulphur in the basic converter, 
furnish heat necessary to keep the metal in a molten state during the blow, 
and so perform the function of fuels. In the roasting and smelting of pyritic 
ores the burning of a portion of the sulphur furnishes a great part of the 
heat necessary for those processes. 

Tar: The use of tar as a fuel is of recent origin, and offers a means 
for the disposal of the excess quantities produced above that required by 
the tar refiners. Having a low ash and sulphur content, it is well suited 
chemically for use as open hearth and heating-furnace fuel. It is a viscous 
fluid at ordinary temperatures. Hence, it must be kept at a relatively 
high temperature both in the storage tanks and feed lines. This heating 
is accomplished by means of steam pipes immersed in the tar. Special 
burners, one type of which is shown in the accompanying figure, of the 
steam or air injector type are required to burn tar properly. Tar carries 
in suspension a great many small carbonaceous bodies, and on standing, 
especially at the lower temperatures prevailing in storage tanks, these 
grow into pitch-like bodies of considerable size, which clog up the burners 
and the small pipe lines of the system. Its calorific power is between that 
of coal and oil, 16000—18000 B. t. u. per pound. This fact, coupled with 
its low cost due to the increased production, tends to stimulate efforts to 
use it wherever possible. 





68 


FUELS 



Petroleum: The only natural liquid fuel, and a material of the highest 
commercial importance, is petroleum, a product obtained from reservoirs 
deep in the earth. Its heating power is much greater than that of coal, 
(The calorific power of crude petroleum=21000 B. t. u. per pound, Coal= 
9000 to 15000 B. t. u. per pound) and it is obtained in immense quantities. 
On distilling, it yields a high percentage of very valuable oils. On this 
account it is used as a metallurgical fuel only where coal is scarce and 
high in price. In using the oil special burners are required, as it must be 
vaporized or atomized and properly mixed with air to insure complete 
combustion. 

Composition of Petroleum: Petroleum is a very complex mixture 
of organic compounds. In small amounts it contains compounds of oxygen, 
sulphur, and nitrogen, but principally it is composed of compounds of car¬ 
bon and hydrogen. Its content of the former element varies from 84 to 
87%, and of the latter, from 11 to 13%, depending upon the locality from 
which it is obtained. 

Hydrocarbons—Generalized, Empirical and Structural Formulas: 

These compounds of carbon and hydrogen found in petroleum are called 
hydrocarbons. They are numbered by the hundred, and a study of their 
composition has shown that they fall into a number of homologous series 
which may be represented by generalized formulas as shown in Table 8. 
In representing these compounds, the empirical, or simplest, formulas are 
often found inadequate, because it frequently happens that two different 
compounds will have the same empirical formula, and that in many com¬ 
pounds the valence of carbon is apparently not a whole number. To 
overcome this defect, the structural formula, which aims to show how the 
molecules are built up, was invented. In these formulas the valence of 
carbon, which is represented by —’s, called valence bonds, is assumed to 
be four in all cases, and it is also assumed that the atoms of carbon have 
the power of uniting with each other to form nuclei to which other 
elements may attach themselves. These formulas are also illustrated in 
the following table: 


























PETROLEUM 


69 


Table 8. The Different Homologous Series of Hydrocarbons. 


Generalized 
Formula of 
Series 

Names Applied 

To Series 

Names of First 
Compound of Series 

Empiri¬ 

cal 

Formula 

Structural 

Formula 

Formula of 
Second 
Member 

CnH2n-(-2 ... 

Methane, Paraffin, 
or Chain Series. 

[Methane 
< Marsh Gas 
(Fire Damp 

ch 4 

H 

1 

H-C-H 

A 

H H 

H-C—6-h 

k k 

OnH 2n. 

Olefine, Ethylene, 
Unsaturated Open 
Chain Series. 

Ethylene. 

C 2 II 4 

H H 
6=6 
k k 

k ir 
6—6- 
k ch 8 


CnH 2n-2.... 

Acetylene Series. 

Acetylene. 

C 2 Ho 

H-CsC-H 

h-c=c-ch 3 

CnH2n-4.... 

First member unk 

nown. 




CnH2n-6. 

Benzene,- 
Aromatic or 

Closed Ring Series. 

Benzene. 

c 6 fj 6 

H 

6 

/ \ 

H-C C-H 

J 1 

H-C C-H 
\ ^ 

C 

H 

C 

/ \ 

H-C C-H 

II 1 

H-C C-CH 
\ ^ 

C 





k 

k 

CnH 2 n-8. 

Not many membe 

rs discovered. 




CnHzn-i 0 .. . 

Not many membe 

rs discovered. 




So on to.... 






CnH2n-3 2.. . 

Not many membe 

rs discovered. 





Hydrocarbons of the series CnH 2 n +2 make up the greater portion of 
the paraffine base of petroleums, as is indicated in Table 9. Members of 
the series CnHan are also constituents of many petroleums, while only a 
few r of the higher members of the series CnH 2 n —2 and CnH 2 n— 4 ,, have 
been found in oils west of Pennsylvania. The aromatic series, CnH 2 n—o, 
occur in small amounts in nearly all petroleums. Occurrence of members of 
the other series is somewhat rare in petroleums, and are in small amounts 
when found at all. 

Fuel Oil and Other P.roducts of Petroleum: The increasing demand 
for gasoline and other petroleum products makes it very undesirable that 
crude petroleum as obtained from the wells be used for fuel. Besides, gaso¬ 
line in a fuel oil is dangerous on accoimt of the increased danger of explosions 
its presence entails. Fuel oil, then, is a very indefinite term that is applied 
to any product of petroleum used for the production of heat or power. 
There are no fixed specifications for it, and consumers order it to suit their 
requirements. The usual grades have a calorific value of about 135000 B. t. 
u. per gallon. The products from many of the oil refineries west of the 
Mississippi River are gasoline, naphtha, kerosene and fuel oil, while Eastern 
refineries usually carry the fractionation of the oil much farther, their output 
being such products as gasoline, benzine, naphtha, kerosene, light machine- 
oil, automobile oils, cylinder oils, paraffin wax and tar, pitch, or coke. 































70 


FUELS 


SECTION IV. 

GASEOUS FUELS. 

Advantages of Gaseous Fuels: The many advantages possessed by 
gaseous fuels make them ideal for many purposes. Owing to their gaseous 
state, they require no labor in handling, and their freedom from foreign 
matter eliminates ash and danger of contamination. As the temperature 
is easily controlled, and the flame can be directed wherever desired, the 
working conditions of a furnace may be kept very uniform. The kindling 
temperature of gases is between 650°C aDd 700°C, and the speed of com¬ 
bustion is practically instantaneous at that point, which fact makes it easy 
to attain very high temperatures. 


Table 9. The Paraffin Series of Hydrocarbons, the Members of 
which are found in Natural Gas and Petroleum of the 
Western Pennsylvania District. 


State at 


Empirical 

Melting* 

Boiling* 

Ordinary 

Name 

Formula 

Point 

Point 

Temp. 



Deg. C. 

Deg. C. 


Methane. 

. ch 4 

—184.0 

—165.0 

m 

0) 

m 

Ethane. 

. C 2 H e 

—171.4 

-T- 93.0 

c3 

O 

Propane. 

. c 3 H 8 

—195 

— 45.0 


Butane. 

V 

. c 4 H 10 

—135 

+ .1 


Pentane. 

. c 3 h 12 

—130.8 

36.3 


Hexane. 

. c 6 h 14 

— 94.0 

69.0 


Heptane. 

. c 7 h 16 

— 97.1 

98.4 


Octane. 

. c s H ls 

— 56.5 

125.5 

• • 

m 

Nonane. 

. CsHoo 

- 51.0 

150.0 

"O 

• rH 

Decane. 

. C 10 H22 

— 31.0 

173.0 

cr 

• i— < 

Undecane. 

. CnH 21 

— 26.0 

195.0 


Dodecane. 

. C 12 H2(j 

— 12.0 

214.0 


Tridecane. 


— 6.0 

234.0 


Tetradecane. 

. c 14 H 30 

+ 5.0 

252.0 


Pentadecane. 

. c 15 h 32 

10 

270.0 


Hexadecane. 


18.0 

287.0 


Octadecane. 


28.0 

317.0 


Eicosane. 


37 0 



Tricosane. 


48 0 



Tetracosane. 


51 0 



Pentacosane. 

. C25H50 

53-54 0 


• • 

m 

Hexacosane. 

. C 2 6H 54 

55-56 0 


• rH - 

Octocosane . 


60 0 


m 

Nonocosane. 


62-63 0 



Hentriacontane. 


68.0 



Dotriacontane. 


70.0 



Tetratriacontane. 


71-72.0 



Pentatriacontane. 


75.0 



See Amencan Petroleum Industry by Raymond F. Bacon and William A. Hamor 
Published by McGraw-Hill Book Company, New York. Also Organic Chemistry by 
A. F. Holleman, Fourth English Edition, published by John Wiley & Sons, Inc., N.Y. 
















































GASES 


71 


Natural Gas is the most remarkable fuel of all. Found in the earth 
under high pressure and free from non-combustible gases, it represents a 
perfect fuel. Upon being regenerated it undergoes partial decomposition 
and is, therefore, never preheated, but with it the highest temperatures 
that are practical are easily obtained by proper manipulation. The sup¬ 
ply of this gas, formerly thought to be inexhaustible, is now declining rapid¬ 
ly, and this fact, combined with its demand for domestic purposes, is forcing 
its use in the metallurgical and other industrial arts to be abandoned. 
Geologically, natural gas is closely associated with petroleum and undoubt¬ 
edly is of similar origin. It is composed of the lower gaseous hydro¬ 
carbons of the paraffin series, mainly methane. 

Artificial Gases are manufactured from coal. The method of manu¬ 
facture depends on the end sought. Thus in retort gases—coal gas and 
coke oven gas—only the volatile products of the coal are utilized for 
gas, while in the gas producer the whole combustible substance of the coal 
is converted into gas. Of these, coal gas and coke oven gas most nearly 
approach natural gas in calorific power and efficiency. Producer gases 
always contain a high percentage of non-combustibles. The advantages 
in favor of the producer are that an otherwise poor fuel may be converted 
into a desirable one, and that all of the fuel is gasified. As to blast furnace 
gases, their utilization under boilers, in gas engines, and in blast furnace 
stoves represents a saving that amoimts to millions in a single year. A 
detailed account of this fuel will be taken up later. Table 10 below shows 
useful data in comparing the various gaseous fuels. 


Table 10. Composition of Gaseous Fuels. 
Representative Analyses 
Percent by Volume 



Natural Gas 

Coke 

Oven 

Gas 

Bench 

or 

Coal 

Gas 

Carbu- 

retted 

Water 

Gas 

Water 

or 

Blue 

Gas 

Producer Gas 

Blast 

Fur¬ 

nace 

Gas 

#1 

#2 

#1 

#2 

Carbon Dioxide, C0 2 

.2 

.2 

1.7 

2.0 

3 0 

3.8 

5.0 

10.6 

12.9 

lliuminants (asC 2 H 4 ) 

.4 

.5 

3.0 

3.7 

10.0 

0 

J 2 

.4 

0 

Oxygen, 0 2 . 

0 

.3 

.1 

.8 

.5 

.5 

0 

0 

0 

Carbon Monoxide,CO 

0 

.5 

3.5 

7.5 

34.0 

43.1 

25.6 

17.6 

26.3 

Hydrogen, H 3 . 

0 

0 

53.9 

48.5 

35.5 

47.5 

10.2 

11.8 

3.7 

Methane. CH 4 . 

77.7 

94.5 

34.6 

33.0 

12.0 

.8 

3.8 

4.4 

0 

Ethane, C 2 H 6 . 

19.4 

0 

not det’d 

not det’d 

not det’d 

0 

0 

0 

0 

Nitrogen, N 3 . 

2 3 

4.0 

3.2 

4.5 

5.0 

4.3 

55.2 

55.2 

57.1 

*Net B.t.u,per cu.ft. 

1027 

868 

518 

512 

465 

277 

148 

135 

94.8 

Gross “ “ “ “ 

1134 

963 

583 

573 

505 

301 

157 

146 

96.7 

Sulphur per 1000 cu.ft 

0 

0 

.8 ibs. 

not det’d 

not det’d 

0 

.1 lbs. 

.15 lbs. 

0 


*Does not include the latent heat of the water formed in combustion. 


Principle of the Gas Producer: While there are many different types 
of gas producer, the apparatus is essentially a vertical cylindrical shaft, 
lined with fire brick, partially filled with coal when in use, through which 
air, or steam and air, are forced at the bottom where combustion of the 
non volatile part of the coal is continuous. In its upward passage the 
carbonic acid gas formed by the combustion of the carbon of the coal is 
reduced, in part, by the incandescent fuel, forming carbon monoxide. 
Part of the water, if steam is used, is also acted upon by the hot coke, 
forming carbon monoxide and free hydrogen, and some methane is 

































72 


FUELS 


obtained from the distillation which the coal undergoes at first. In case 
steam is used with the air the producer gives a gas which may vary in 
composition about as follows: 

Carbonic Acid...COo— 5 to 9% 

Carbon Monoxide.CO —18 to 27% 

Methane.CH 4 — 2 to 4% 

Hydrogen. H 2 —10 to 18% 

Nitrogen. N 2 —48 to 55% 





SHr* 






mgmm 


O'. 




■B Hi 


Fig. 10. Sketch. Section Through Gas Producer. 
































THE GAS PRODUCER 


73 


Factors Affecting the Efficiency of the Producer: The greatest 
efficiency of the gas producer is attained when all the oxygen of the injected 
air is caused to combine with carbon to form only carbon monoxide, provided 
the excess heat thus generated is also made available. In practice these 
results are never accomplished entirely, but efforts to attain them have 
revealed the fact that they can be most nearly approached by carefully 
regulating the temperature, by maintaining perfect imiformity of the 
working conditions, and by injecting steam with the air. All these objects 
are accomplished in fairly efficient degree in the Hughes mechanically 
poked producer, a brief description of which follows: 

The Hughes Producer as an Example of Mechanically Poked Pro** 
ducer: This producer, a vertical section of which is illustrated in the 
accompanying sketch, is a cylindrical steel shell, % n thick, lined with 
9 inches of first quality fire brick, and closed at the ends with water sealed 
tops and bottoms. When ready for use it sets with its base resting on five 
wheels which are mounted on a frame carried on a concrete foundation. 
By means of gears connected to a driving mechanism, it is rotated over 
these wheels, the speed of rotation when in use being 1/10 r. p. m. The 
top plate is a steel casting riveted to the charging floor, under which the 
producer itself revolves. It contains the openings for the gas outlet, the 
hoppers, the poker and the observation holes. There are two hoppers, 
through which coal is fed to the producer, one on each side of the outlet, 
but they are at different distances from the center of the producer to 
help provide even distribution of the coal. A bell valve closes the 
base of the hopper, and when this bell is dropped to dump the 
coal into the producer, the hopper may be closed by sliding a circular 
plate over its top. There are several holes three inches in diameter at 
various points in the top seal for observing the condition of the 
fire, and for poking out clinkers; these holes are closed with water 
sealed caps. The poker is a round hollow steel casting with a forged 
steel tip. It is six feet in length and tapers from eight inches in diameter 
at the top to five inches at the tip. The poker and its trunnions are water 
cooled, the water being admitted through the trunnions, then passing 
through the poker to the top plate which is covered with the water to a 
depth of five inches. From the top plate the water flows to the top seal, or 
trough, around the top plate, then through a drain pipe to the water seal 
in the ash pan. The top of the poker is enclosed in a gas tight mounting, 
and is so mounted that the poker is swung back and forth through an arc 
of about 35° by means of eccentric connections from the producer rotating 
mechanism. A full stroke of the poker carries its tip from the center to 
the side wall of the producer, and is timed to occupy 3.21 minutes, thus 
allowing 3.1 strokes in one revolution of the producer. The result of the 
rotating motion of the producer and the backward and forward action of 
the poker is to produce a series of semi-ellipses, so that the poker covers, 
in a period of 70.72 minutes, or 22 strokes, practically the entire area of the 






74 


FUELS 


shell. The bottom of the vessel serves as an ash pan, which must also 
be water sealed. To form this seal the bottom is made in the form of a 
circular trough, which is attached to the main shell of the vessel so that 
its outer rim, or lip, extends several inches beyond this circumference of 
the shell. Into this trough the sealing shell of the producer projects to 
within five inches of the bottom. Since this construction leaves the central 
portion of the bottom within the producer somewhat cone shaped, the 
ashes are deflected toward this five-inch opening at the bottom of the trough, 
where they may be removed through the water which flows from the top 
and fills the trough to prevent the escape of gases. The steam blower is 
inserted through the center of the bottom and extends some twenty inches into 
the producer, where it is capped by a conical hood to prevent it from becom¬ 
ing choked with the ashes. The mixture of steam and air is admitted just 
beneath this hood through three rows of small openings to provide for 
equal distribution of the blast. The ratio of steam and air is controlled 
by the openings at the bottom of the blower, but the quantity of the mixture 
admitted to the producer is regulated by the steam pressure, which may 
be changed at will by the operator from the charging floor. 


Conditions and Reactions: An understanding of the principle and 
the operation of the producer is much clarified by a study of the reactions 
and conditions prevailing in it while it is in use. A study of the conditions 
show that there are three zones or belts of action in the producer, known 
as the distillation or top zone, the reaction, or middle, zone, and the 
combustion, or bottom, zone. Then, below these zones is the inactive, or 
ash, zone. Thus, upon being charged into the producer, the raw coal is 
first subjected to a distillation very much as in the process of coking. In 
this top zone the volatile products are driven off, and the coal is converted 
into a kind of coke, which will have then reached the reaction zone. Some 
of this coke, passing through the reaction zone unchanged, reaches the 
region just over and around the hood of the blower. Here it meets the 
incoming air, and having been heated to above the kindling temperature, 
combustion takes place, whereby all the remaining carbon is consumed 
according to this simple reaction, C-t-0 2 =C0 2 +heat. The carbon dioxide 
gas thus generated, together with the undecomposed steam and other gases, 
rises at once into the reaction zone. Here the coke, having been heated 
to a high temperature from the heat liberated by the above reaction, acts 
as a reducing agent toward both carbon dioxide and water, thus, C0 2 +C+ 
heat=2 CO and H 2 0+C4-heat=H 2 +C0. It will be noted that both 
+hese reactions absorb heat, but that only the second is under control and, 
hence, available for lowering the temperature in the producer. The 
reduction of all the C0 2 formed in the combustion zone has never been 
brought about, so that a small quantity is always present in producer gas. 
The relative amounts of CO, H 2 and C0 2 in the final gas depends to a 
great extent upon the manipulation of the producer. As to the other com- 





SOLID NATURAL FUELS 


75 


ponents of this gas, the nitrogen, being introduced with the oxygen as air, 
cannot be controlled, while the hydrocarbons such as CH 4 and C 2 H 4 repre¬ 
sent products of the distillation. 

Operation of the Hughes Producer: The ideal conditions in a Hughes 
producer are realized when the combustion zone extends to about a foot 
above the top of the blower hood; when the reaction zone is from one and 
one-half to two feet thick; when the distillation zone is from one-half to 
one foot thick; -when the conditions are such that the ash, the coke 
and the coal occur in level zones; and when the amount of air and steam 
are so adjusted that the fuel is properly burned without excess of any of 
the undesirable components in the final gas. The necessary air is injected 
into the producer by a steam jet. Thus the steam serves the two-fold 
purpose of injecting the air and of controlling the temperature in the pro¬ 
ducer by absorbing heat, during its decomposition, which later appears as 
potential energy in the gas. This lowering of the temperature, combined 
with the disintegrating effect of the steam upon the ash, tends to prevent 
clinkering. If too much steam be used, the temperature in the reaction 
zone will drop beloW normal, the CO will be low and the percentage of 
hydrogen will be high. This condition causes the gas to burn with a short, 
intense non-luminous flame that has a detrimental effect upon the brick 
work of the furnace in which it is used, especially upon the ports and roof 
of the open hearth furnace. But the judicious use of steam may increase 
the efficiency of the producer to 80 or 85% of the heating power of the fuel. 
The experienced operator judges the quality of the gas by its appearance, 
striving for a dense yellowish blue gas. The greatest trouble in operating 
arises from the accumulation of unburned carbon and fine ash in the mains, 
which must be cleaned out at regular intervals. The mains are brick 
lined and are fitted with numerous dust catchers, or man holes, to afford 
access for cleaning. 


SECTION V. 

THE SOLID NATURAL FUELS. 

Analysis of Solid Natural Fuels: Upon examination all the solid 
natural fuels are found to consist of combustible and non-combustible 
materials. The combustible portion is composed mainly of carbon and 
hydrogen, and the constituents of the non-combustibles are water and a 
mixture of mineral substances called ash. By the gradual application of 
heat without access of air, the water is first expelled, which is followed 
closely by the combustible volatile matter, and there remains a non-volatile 
mass composed of carbon, called fixed carbon, and ash. Upon admitting 
air, the fixed carbon burns readily, leaving only the ash. A similar process 
carried out so as to determine the amounts of these four classes of materials 
is called a proximate analysis. There are two general methods for making 
a proximate analysis, depending upon whether or not it is desired to separate 




76 


FUELS 


the volatile matter into its constituents. These are often referred to as 
the American and the European methods, the latter being also called the 
progressive distillation method. The determination of the percentages of 
the various elements present in the fuel constitutes an ultimate analysis. 
The following analysis of a coal by each of these three methods will illus¬ 
trate all the points mentioned, and help to show the importance of the 
chemical analysis. 


Table 11. Analysis of a Solid Fuel, Coal, by the Three Different 

Methods. 


fAsh 


7.16% 


Proximate 

Analysis, 

American 

Method 


Fixed Carbon.... 59.98 
Volatile Matter... 32.86 

Total.100.00% 

Total Sulphur. ... 1.02% 

Phosphorus.005% 


f 


Proximate 
Analysis, 
Progressive < 
Distillation 
Method 

\ 


Coke 


/Ash.... 
\ Carbon 


Tar 


7.160% 

59.980 

5.420 


Free NH 3 .285 

Comb. NH 3 . .041 

Moist. 4.765 

Oxygen. 1.046 

Volatile Sulphur .313 
Crude Benzol... 1.353 
Gas. 19.640 


Total.. .100.003% 


fAsh . 7.16% 

|C . 79.41 

Ultimate Analysis' ^. 

0. 6.03 

S. 1.02 


100 . 22 % 


Wood: This very interesting substance is composed mainly of 
cellulose, CcH 10 O 5 , -a compound formed in the tree or plant from water 
taken up from the soil and carbon dioxide from the air. The change is 
wrought mainly in the leaves of plants through the agency of sunlight. 
Wood, then, represents potential energy, the original source of which is 
the heat from the sun, and it, in turn, is the source of all the natural solid 
fuels. It was the first fuel used by man, and for centuries was the principal 
one. In metallurgy it has been supplanted by coal, though for some purposes 
it is still used, mainly in the form of charcoal obtained by the destructive 
distillation of wood. The calorific power of dry wood is about half that 
of good coal. 


























PEAT, WOOD, COAL 


77 


Peat is of little value as a metallurgical fuel. It finds extensive use 
in Europe as a domestic fuel, and the better grades may be successfully 
employed in gas producers. Its chief interest lies in the fact that it is the 
first step in the formation of coal. Peat results from the decomposition 
of wood substance out of contact with air. It is formed in swamps and 
marshes from water plants of all kinds such as algae, mosses, sedges, rushes, 
reeds, shrubs, like willows, and even trees. A species of moss called 
sphagnum is especially important in the formation of peat. It grows on 
the surface of still and shallow waters with only a small portion in air, 
and as it grows the submerged portion extends farther and farther beneath 
the surface until the bottom is reached. Starting growth near the shore 
of shallow lakes, it gradually extends into a lake until the whole basin 
is filled with soft carbonaceous matter, and a bog results. This growth is 
followed by larger growths, until the former lake is packed with carbonaceous 
matter. The accumulation being submerged, the carbon compounds of the 
plants are slowly decomposed, by which process the carbon is isolated, 
though a part escapes w r ith hydrogen and oxygen as marsh gas and carbon 
dioxide. The reaction is represented thus: 

6C 6 Hio05 = 7 CO2 T* 3 CH4 + 14 H2O + C20H2OO2 

Cellulose or Carbon Marsh Water Peat Substance • 

Wood Substance Dioxide Gas 

In certain geological periods, particularly the carboniferous, the 
conditions being more favorable for plant growth of this kind, the processes 
described proceeded more rapidly than at present, with the result that 
marshes of great depth and area were filled with vegetable growths. These 
carbonaceous deposits were subsequently submerged through vertical 
movements of the earth’s crust, in which position they became covered by 
deposits of sedimentary rocks. Later movements of the earth’s crust 
raised many of these deposits up out of the sea. In the meantime the peat 
had been changed into coal. 


Lignite and Brown Coal, geologically and chemically, occupy positions 
intermediate between peat and coal. They were formed between the 
Quaternary and Jurassic periods and are widely distributed. They have 
low calorific power, and some kinds contain as much as 15% of water. 
They are sharply distinguishable from peat, but grade into coal so gradually 
that no one has attempted to distinguish between the oldest lignite and 
the youngest coal. The relation between vegetable and mineral fuels aie 
more clearly shown by the accompanying table (12) and diagram (Fig. 11). 





78 


FUELS 


Table 12. Approximate Analyses of the Different Solid Fuels. 



Air Dried 
Wood 

Air Dried 
Peat 

Lignite 

Bituminoua 

Coal 

Anthracite 

Coai 


% 

07 
/ 0 

% 

% 

% 

Yol. M . . 

42-40 

30-60 

30-45 

20-45 

.5-6 

Fixed C.. . . 

39-41 

11-40 

45-50 

40-85 

S5-92 

Ash. 

Moisture or 

.15-2 

3-75 

4-15 

4-20 

2-15 

W ater... . 
C. P. (Cals. 

20-25 

6-20 

10-15 

1-6 

.5-4 

per Kilo). 

4600-5000 

2000-5000 

3000-6000 

7000-9000 

9000-9500 



Fig. 11. Graphic Representation of Transformation of Fuels. 






























































PEAT , WOOD, COAL 


79 


cd jn 

g-2 g 

T3*< 

a 


fj 

-2 
O c$ 

§ a 
2 a 

o 05 


o ^ 

O a; 
S3 r= 

£ a 


Periods 

and 

Chief Events 


Quaternary 
Glaciers in N. E. 


It HU l~li II 


Tertiary 
Rocky Mountains 


Formed 


Cretaceous 
Rapid Erosion, West 


Order 

of 

Strata 




mm 




Deposits 

of 

Valuable Minerals 


Peat in East 

Lignite in West 
Petroleum in Tex. and Lou. 


mnziiii] 


\/ S T' ■* 






Lignite in West 

Gold and Silver in West 

Oil and Gas in Wyo. and Cal. 




vnnnim 


Mountains West 
Jurassic 

Warping of Surface £ 


rv-.'.o'v-y 


wvxww 

awwn w. 


Triassic 


3^ 

M 




Lignite in West 

Chalk in So. W. 

Petroleum in Cal., Wyo., Tex., 
Colo, and La. 

Potomac Carbon Rock 

Petroleum in Wyo. 

Limestone—Wyo. and Utah 


Slow Folding East 

Surface Alternately 
Rises and Sinks 


—Coal in Va. 

Petroleum in Wyo. 
Pock Sait of Texas 


kWivi v.<vi 

uwrcwvw 



Petroleum both East and West 


Coal 
Coal 

Coal h Pennsylvania District 
Coal 
Coal 
Coal , 

Gypsum 

Limestone in Middle West 


Oil, Gas-Pa., W.Va.,0.,N.Y.Ind. 

Limestone, East 

Limestone, East 
Sand Stone 


Carboniferous Period 
Coal Beds 
of 

Western Penna. District 


o a 
> o 


a> o 
Pif-i 


Limestone, East 
Clinton Iron Ores, Ala. 
Oil-Gas in N. Y., 0.. Ind., Ill. 
and Ky. 


— ~Z~Z.'Z\ Rock Salt in N. Y. 
Limestone 
Zinc and Lead 


Sand Stone 
Limestone 


Limestone 

Lake Superior Iron Ores 


Graphite 

Igneous Rock 


Name 


o 

Tt< 


a 


O 

co 


Waynesburg 


o 

CO 

CD 


CO 

ID 


o 

ea 


rfi 


O 

CO 


Sewickley 

Redstone 

Pittsburgh 


Thickness 


Max. 


Min. 


10 ft. 


6 ft. 
6 ft. 

9 ft. 


Upper Freeport 
Lower 

Upper Kittanning 
Middle 

Lower 

Clarion 
Brookville 


8 ft. 

5 ft. 

4 ft. 
3ft. 

8 ft. 

2 ft. 

5 ft. 


6 in. 


3 ft. 
3 ft. 

5 ft. 


3 in. 
? in. 


Fig. 12. Diagram Depicting Geologic Periods in which Gas, Oil and the 
Valuable Minerals are Found in the United States. 
































































































































80 


FUELS 


Coal: This mineral, on account of its availability, adaptability, and 
high calorific power, has become the chief source of energy at the command 
of man. Used both in its natural state and in prepared forms, it constitutes 
the chief metallurgical fuel; and the high state of development of certain 
processes, like that of the blast furnace, for example, have been possible 
only through the peculiar properties of this remarkable substance. Its 
origin and history is as remarkable as its properties, and though these 
subjects belong to geology, they are of interest to the metallurgist because 
they emphasize the need of conserving the fuel. While it has been deposited 
in immense amounts, the supply is exhaustible and practically fixed, since 
the rate of consumption is many times the rate at which it is being formed. 
In this connection a study of Fig. 12 will be found interesting. 

Bituminous Coal: All coal in the natural state may be looked upon 
as being composed of coal substance, ash, and hydroscopic water. 
Bituminous coals, on account of their peculiar properties, are the chief 
source of metallurgical fuels. The coal substance of these coals is decom¬ 
posed by distillation into carbon and a mixture of volatile compounds. 
During this process some kinds fuse into a pasty mass, leaving at the end, 
when all volatile matter has been, expelled, a strong but porous mass called 
coke. It is not known what the coking properties of coals depend upon. 
Coals very much alike in physical appearance and chemical composition 
may show widely differing coking qualities, while others differing in both 
these respects produce cokes of equal quality. During the coking process, 
some coals expand while others contract. This point is an important one 
in by-product practice, because expansion wedges the coke in the oven, 
making it difficult to remove, and causing damage to the oven walls. 

Ash in Coal: The ash in coals is also an important factor in their 
valuation. Aside from decreasing the calorific power, it affects the coal in 
other ways. In steam coals the composition of the ash may be such that 
it fuses at a low temperature, thereby forming large clinkers; or it may be 
practically infusible, resulting in no clinker, with the result that a suitable 
bed of coals cannot be kept on the grate, due to the fineness of the ash. 
To cite a concrete example, a certain coal in the Pittsburgh District pro¬ 
duced ash of approximately the following composition: SiC> 2 , 45%; AI2O3, 
24%; Fe 2 0 3 , 21%; CaO, 7%; MgO, 2%; P 2 0 5 , .6%. Such an ash is moder¬ 
ately fusible, and so is most desirable. In the ash is found the phosphorus, 
which determines whether coke made from a certain coal shall be used for 
making Bessemer or basic iron. The sulphur is also important. In coal 
it is present as organic and iron sulphide. In coking, about half of this 
sulphur is given off with the volatile products, and about half remains in 
the coke as FeS or Fe 7 S 8 and S. When the coke is burned these sub¬ 
stances are completely changed, the iron being oxidized to Fe 3 0 3 , or 
Fe 3 C >4 and the sulphur to SO 2 . Often a seam of good quality coal is 
divided or cut horizontally by deposits of slaty material known as bone 




PULVERIZED COAL 


81 


coal, binder, horse back, etc., all of which must be mined with the coal. 
Where these conditions exist, it is necessary to clean the coal by picking, 
jigging, or washing. As a rule the purest coal is in the middle of the 
seam. Phosphorus in particular occurs mainly at the top. The top and 
bottom will always contain the highest percentages of ash and sulphur. 


SECTION VI. 

PREPARED SOLID FUELS. 

Powdered Coal: It has long been known that the combustion of finely 
pulverized coal presents features similar to those encountered in burning 
gases. When mixed with air and ignited, it explodes; and when it is blown 
into a heated chamber with sufficient quantity of air, complete and rapid 
combustion approximating that of the fuel gases ensues. These facts led 
to the idea of using pulverized coal as a substitute for gaseous fuels. Though 
first attempted about 100 years ago, no progress was made in its use until 
recently, owing to the difficulties of securing the proper conditions, and also 
to the abundance of other desirable fuels. Although still in the experimental 
stage, it is now used very successfully and gives promise of replacing gaseous 
fuels for metallurgical and many other uses. 

Requirements: The use of powdered coal necessitates meeting the 
following requirements: 

1. With the apparatus now in use, only high volatile coals (volatile 

matter over 30%) may be used. 

2. The coal must be very finely pulverized. Approximately, 70% 

should pass a 300 mesh sieve, 80% a 200 mesh, and 95% a 100 
mesh. 

3. The dust must be injected into the furnace in such a manner that 

each particle enters the combustion chamber surrounded with 
air. 

4. If the coal is to be used in regenerative furnaces, special checker 

work that will permit of easy cleaning is required A high 
percentage of ash is drawn out with the gases, which quickly 

• clogs ordinary checkers. 

5. Careful regulation of draft to give a low velocity of the air and gases 

is necessary to secure complete combustion, since the dust burns 
more slowly than gases. This precaution also prevents rapid 
clogging of checkers when the fuel is used in regenerative furnaces. 

The pulverizing of coal makes it necessary to dry it thoroughly, and 
necessitates the installation of special appliances for handling the dust, 
which can be done only through pipes and tightly closed bins. Two general 



82 


FUELS 


methods of handling are available, namely, the worm screw and the 
pneumatic. The third requirement calls for special burners, so constructed 
as to permit of the regulation of the amounts of both air and dust and the 
adjustment of the direction of the flame. The equipment will consist, then, 
of a dryer, a pulverizer, separator, conveyors, bins, burners, and air com¬ 
pressors, with the necessary motors or engines. Added to these, in many 
cases, will be the special regenerators previously mentioned. 

Advantages of Powdered Coal: It is adaptable for use wherever large 
amounts of fuel are consumed, and many claims as to its advantages are 
made. As compared with producer gas to fire open hearth furnaces, for 
example, it is said to be as efficient and convenient as the gas and to give 
a more regular supply of heat. It is cheaper to prepare than producer gas, 
increases the production of steel 10% or more, and reduces the loss by 
oxidation—all without contamination of the steel from impurities in the 
ash, if proper conditions prevail. 

The Sharon Plant: The appliances for preparing and burning the coal 
vary in form and method. A brief description of the installation at the 
Sharon Works of the Carnegie Steel Company, which is equipped to supply 
three 40-ton basic open hearth furnaces, may serve as an example of one of the 
methods employed in its use. This plant was the first of the Carnegie 
Company’s to use this fuel in the open hearth. The installation is that 
of the Raymond Bros, of Chicago, who employ an impact pulverizer with 
an air-separating system. 

Description of Pulverizing Plant: The building in which the pulver¬ 
izing is done is separated from the open hearth building by about 75 yards. 
Outside this building, is a small trestle storage bin to which the coal, 
crushed to pass a one inch ring, is delivered from the cars. From this bin 
the coal is delivered by a motor driven belt conveyor to the elevated end 
of a revolving cylindrical dryer, about 30 ft. long and 5 ft. in diameter, 
inclined at an angle of about 10°. By revolving this dryer, the coal is 
caused to pass slowly toward the lower end, and in so doing it is stirred 
and scattered in the cylinder, so as to be thoroughly dried by a forced 
circulation of an atmosphere of hot gases from a small brick furnace located 
at the elevated end of the furnace. These gases are conducted from the 
furnace to the lower end of the dryer by a stationary flue, about 18 inches 
in diameter and concentric with the external cylinder. Upon reaching the 
lower end of the dryer, the coal is discharged into a hopper bin from which 
it is elevated vertically a distance of about 20 ft., by means of belt buckets, 
to a 25-ton storage bin. From this bin it is fed by gravity to the pulverizer, 
through the opening of which it is mechanically fed at a rate adjusted to 
the speed of the pulverizer, which has a capacity of 5 tons per hour. 
Through a pipe, about 16 inches in diameter, leading from the top of the 
pulverizer, the finest dust is pneumatically elevated to a cone shaped cyclone 







POWDERED COAL 


83 


separator, about 6 ft. in diameter and some 70 ft. above the pulverizer. 
The mixture of air and dust enters at the top of the separator on a tangent, 
and is, therefore, given a swirling motion at the same time that its velocity 
is reduced. The air, carrying very little dust, is forced out through a pipe, 
about 24 inches in diameter, inserted in the center of the top of the separator. 
Through this pipe the air is returned to the pulverizer, completing the 
circuit. By this arrangement the dust in the air, on entering the separator, 
is subject to the double effect produced by the whirling motion and the 
reduction in speed—namely, centrifugal force and gravity—with the result 
that it is precipitated upon the inclined wall of the separator and falls out 
at the bottom through a rectangular chute (about 6"x8") leading vertically 
down to a 12-inch screw conveyor, which carries the dust to the distributing 
conveyor located above the open hearth furnaces. This conveyor, extending 
at right angles to the 12-inch one, distributes the dust to six 9-ton bins, one of 
which is located above and at each end of each furnace. The bottoms of 
these bins are connected to small 4-inch screw conveyors, driven by variable 
speed motors, which feed the dust to the burners at any speed desired. 
Falling vertically through a 4-inch pipe, the dust passes through a 1-inch 
opening into a 2-inch horizontal pipe where it is met at right angles by a 
jet of compressed air. This jet blows the dust through the 2-inch pipe a 
distance of about 8 inches into a 5-inch nozzle, some 16 inches long, where 
it is mixed with a larger volume of air under the low pressure of 16 inches 
of water. The velocity of this air is sufficient to carry the dust into the 
furnace through a water cooled opening, where it comes in contact with 
regenerated air and is completely burned. The air blown in through the 
burner is about 25% of the total required for combustion. 

Clairton and Homestead Plants: More recent and much larger 
installations for powdered coal have been made at Clairton and Homestead. 
The plant at Clairton is equipped to supply 5 of the 16 sixty-ton open hearth 
furnaces, while the one at Homestead is designed to furnish fuel for the 
whole of the No. 3 open hearth plant, which consists of twenty-four 60-ton 
furnaces. At both these plants the drying, pulverizing and conveying 
equipment is practically the same in kind as that used at Sharon, but a 
different type of burner is used. While the burners at Sharon are 
mechanically fed, at Clairton and Homestead they are wholly pneumatic. 
The principle of the pneumatically fed burners is easily understood from a 
description of the apparatus. The arrangement of the burner is shown in the 
accompanying drawing, Fig. 14. It consists of a delivery pipe, 134 inches in 
diameter by 2 feet 3 inches long, a compressed air nozzle, and a ‘ ‘cross, ” which 
is a small casting containing a 3-inch cubical cavity. The nozzle, % inches in 
diameter inside, passes through one side of the cross, then across the cavity 
and enters the delivery pipe inserted in the opposite side, so as to give an 
injector effect that draws the dust through the one inch opening shown by the 
dotted lines of the drawing. A This opening is connected by a suitable pipe 
to a cast iron feeder box attached to the bottom of the storage bin, located 




84 


FUELS 


some ten feet away. This box, about twelve by fourteen inches in cross 
section, is in the form of an elbow. One end is bolted to the bottom opening 
of the bin, while the other is closed with a steel plate. The pipe leading 
to the burner is inserted in an opening on the top of the horizontal portion 



of the box. With all connections between burner and feeder box tight, the 
operation of the burner is very simple. By means of a valve, not shown 
in the drawing, compressed air delivered under a pressure of about eighty 
pounds may be admitted through the nozzle, when the suction draws the 



















































































COKE 


85 


coal dust from the feeder box and blows it through the delivery pipe into 
the furnace. It will be observed that the design of this burner is based 
upon the principle that the quantity of fuel dust injected into the furnace 
is controlled by the quantity of air passing through the injector. The 
threaded hole in the top of the cross provides a means of attaching the 
burner to its supports. 

Coke. Coke is the residue that remains after certain bituminous coals 
have been subjected to destructive distillation. Owing to its peculiar struc¬ 
ture and physical, or mechanical, properties, it has become the chief metal¬ 
lurgical fuel. All coke possesses a cellular structure, but there is a wide 
variation in the degree of porosity for different cokes. Likewise the hardness, 
brittleness and strength of coke are subject to wide variations. Coke for 
blast furnace consumption should be of a porous character to admit of ready 
combustion, and it must at all times be sufficiently strong to resist pressure 
due to the heavy burden without crushing. In chemical composition, the 
different cokes show a similar wide variation, though for metallurgical 
purposes the fixed carbon, which is the only constituent sought, will con¬ 
stitute 85 to 90% of the coke. The other constituents, roughly stated as 
ash, sulphur and phosphorus, are impurities. The per cent, of phosphorus 
in the coke determines whether the coke is suitable for making Bessemer 
or basic iron. For the former grade, modern practice requires that the 
phosphorus content of the coke must not exceed .018%. The sulphur content 
ranges from .60% to 1.50%, though it is evident that both the sulphur and 
ash should be kept as low as possible. 

Methods of Manufacturing Coke: There are two methods for the 
manufacture of coke, known as the beehive and the by-product, or retort, 
process. In the beehive process, air is admitted to the coking chamber 
for the purpose of burning therein all of the volatile products of the coal 
to generate heat for further distillation. Incidentally, some of the fixed 
carbon of the coal is also consumed. In the other method, the coking 
chambers are air tight, and the necessary heat for distillation is supplied 
from external combustion of the volatile products of the coal; and with 
modern ovens, properly operated, only about half of the gaseous matter 
from the coal is used in carrying on the coking process. While the beehive 
process was, until recently, the leading method for the manufacture of coke, 
it is fast being replaced by the by-product process. The processes of manu¬ 
facture have very little effect on the quality of the coke, but if there is any 
difference, the latter process has the advantage. There is, however, a 
difference in appearance, due mainly to the difference in the coking temper¬ 
ature of the two processes, that of the by-product being much lower than 
the beehive. In general, beehive coke is silvery gray in appearance, while 
by-product coke is of a much darker color. As examples of these two 
methods of coking, the following brief descriptions of plants are to be taken 
as typical of the best modern practice for each process. 





86 


FUELS 


SECTION VII. 

THE BEEHIVE PROCESS FOR THE MANUFACTURE OF COKE. 

The Continental No. 1 Plant of the H. C. Frick Coke Company 

may be cited as an example of beehive coke practice. It is located near 
Uniontown, Pa., in the southeastern part of the famous Connellsville coke 
region. It consists of a coal mine and a coking plant of 400 beehive ovens. 

The Mine: Since the coal bed here lies about 330 feet below the 
surface, the coal is mined through a shaft. Although some gas is given 
off as the coal is mined, it is prevented from collecting and thus becoming 
dangerous by a very efficient system of ventilation, which permits the 
installation of electrical appliances for lighting and the use of both pick 
and machine methods of mining. The coal seam in this mine varies from 
seven to nine feet in thickness, but in mining the coal, about four inches 
at the bottom and from four to eight inches at the top, being high in ash, 
sulphur and phosphorus, is allowed to remain in order to improve the quality 
of the coke. Incidentally, this top discard also helps to support the gob, 
an easily dislodged and treacherous slate-like formation lying between the 
coal and the hard overlying rock deposit and forming the roof of the mine. 
The average output of the mine is twelve hundred net tons per day. For 
transporting this coal through the mine underground, a combination system 
of electric and rope haulage is employed from certain points, while horses 
are used to distribute empty cars to and assemble loaded cars from the 
various working places. From these assembling points the loaded cars 
are moved by electric locomotives in trains of thirty cars each to a sub¬ 
station, where they are attached to the rope haulage which pulls them to 
the foot of the shaft. Here they are hoisted, one at a time, to the tipple 
and automatically dumped into bins. From these bins the coal is loaded 
by chutes into electric larries which convey it to the ovens some hundred 
yards away. Each larry holds sufficient coal to charge one oven, and it 
will be noted that run-of-mine coal is used for coking, no crushing nor 
preparation of any kind being necessary. 

Construction and Arrangement of the Ovens: As to the essential 
features of construction, the name beehive is literally descriptive of the 
form of the beehive oven. The dome-like chamber, built on a suitable 
foundation, is constructed of highly refractory brick, has a flat but 
slightly sloping bottom, an opening in the top, the runnel head,” through 
which the coal is charged and the products of distillation and combustion 
escape, and an arched opening at the bottom, called the door, through 
which air is admitted for combustion and the coke is watered and drawn. 
In general, the dimensions of different ovens vary a great deal. The ovens 
at this plant are each 12 feet 3 inches in diameter and 8 feet high from the 
bottom to the top of the dome, inside dimensions. Of this height, the side 
wall, built of fire brick, rises vertically a distance of 27 inches, and is capped 





BEEHIVE COKE 


87 


by the crown which is built of silica brick. Except in the case of the special 
brick used about the openings, the brick in these walls are of standard 
size and are laid ends in and out, thus making both the side wall and the 
crown wall approximately 9 inches thick. Finally, this brick structure is 
covered on the outside and up to the level of the “trunnel head,” which is 
14 inches in diameter, with loam or rough clay which acts as an insulator of 
and a store house for heat. For retaining this loam covering, there are in 
general three different arrangements of ovens as follows: (1) the bank 
system, in which the ovens are built in single rows against a bank of earth, 
natural or artificial, thus making it necessary to build but one retaining wall 
along the front of the ovens; (2) the single block system, which consists 
of a single row of ovens with retaining walls at both the front and back; 
and (3) the double block system, in which the ovens, in a double row, are 
built back to back or staggered with a retaining wall extending along the 
front of each row. At this plant there are four double block batteries and 
two batteries of banked ovens. 

Waste Heat System: One battery of the banked ovens, forty in number, 
is arranged for utilizing the waste heat from the products of combustion 
to generate steam. For this purpose a large tunnel is constructed in the 
bank some 10 feet back of the ovens and parallel to the battery. This 
tunnel is connected to each oven by means of a small flue, which conducts 
the hot gases out of the oven from an opening sufficiently above the side wall 
to prevent its being closed by the largest charge of coal used. Each flue 
is provided with a damper for closing off the draft during the period the 
oven is being watered, drawn and charged. From the battery, the tunnel 
passes to the boiler house, where branches conduct the hot gases through 
the fire boxes and flues of the boilers which are connected to a common 
stack, about 100 feet in height to cause the proper draft. During the coking 
period, the “trunnel head” is necessarily kept tightly closed. Owing to the 
increased draft, these ovens are inclined to run up a little higher temper¬ 
ature than the ordinary oven, so that the temperature in the tunnel is 
high, sometimes reaching 1500°C. A maximum of about 800 horsepower 
is generated from the waste heat from this battery of forty ovens. 

Charging the Ovens: The ovens are charged as soon as practicable 
after drawing, so that the stored up heat from the previous charge will be 
sufficient to start the coking process. In the case of new work, the ovens 
must be heated up gradually to a coking temperature by means of wood 
and coal fires, after which period small charges of coal for coking are used 
until the ovens reach normal working conditions. With the oven in 
readiness for charging, the door is bricked up to within about one and one 
half inches of the top; and the charge, which consists of six and one half 
tons of coal for 48-hour coke and eight tons for 72-hour coke, the latter 
being made over the week-ends, is dropped through the “trunnel head” from 
the larry above, leaving the coal in a cone shaped pile in the oven. In 




S8 


FUELS 


order to secure uniformity in the coking of the coal, this pile must be 
levelled so that the coal will lie in a bed of uniform depth over the entire 
bottom of the oven. This result is attained by means of an electrically 
operated leveling machine, which is moved from oven to oven on the 
same tracks that the charging larry uses. The essential part of this 
machine consists of a vertical rod and sleeve, on the lower end, or head, 
of which is mounted two collapsible leveling arms. By means of suitable 
gear connections with an electric motor, this apparatus, with the head 
closed, may be mechanically lowered through the “trunnel head” upon the 
apex of the pile of coal, when the rod and sleeve are made to revolve and 
the leveling arms are at the same time slowly extended. These motions, 
combined with the continued lowering of the head, distribute the coal to a 
uniform depth in a very few minutes. In works not equipped with this 
machine, the leveling is accomplished by means of a large long-handled 
scraper, operated, by a laborer, through the door of the oven, which is 
purposely bricked up to about only two-thirds of its height at the time of 
charging. 

The Coking Process begins very soon after the levelling is completed, 
as the ovens retain enough heat in the brick of the walls and the loam backing 
to start the distillation of the volatile matter of the coal. As more and more 
heat is conducted through the walls from the hot loam backing, the tem¬ 
perature of the interior of the oven soon reaches the kindling point for these 
volatile gases, which, in the presence of the air admitted to the oven, ignite 
with a slight explosion at first, then continue to burn quietly in the crown 
of the oven, or, as small candle-like flames at the surface of the coking 
mass, thus supplying heat to continue the orocess. The coking proceeds 
from the top of the coal downward, so that the coking time depends mainly 
upon the depth of the coal. The volume of volatile matter thus rapidly 
approaches a maximum, which is maintained for a period, then declines to 
practically nothing, hence the burning of this volatile matter must be 
regulated by gradually closing up the opening at the top of the door for the 
admission of air. This regulation is very necessary to maintain the 
temperature at a maximum, and conserve coke, as an excess of air at the 
beginning of the coking period tends to cool the oven, and later con¬ 
sumes the carbon of the coke. The yield is also reduced by improper 
leveling. If the coal is not of uniform depth to begin with, the thin portions 
coke through before the thick, and some of the coke in the thin sections 
is consumed while the coking of the thick portions is being completed. 
On the other hand, if the process be stopped w r hen the thin areas have 
coked through, there will be a loss due to green butts on the thick areas. 
It will be recalled that the coal assumes a semifused, or pasty, state during 
the coking process. The result to be expected from such behavior is that 
the coke would be found in a continuous mass, or cake, at the end of the 
process; but, due to expansions and contractions of the mass in coking and 
on cooling, the cake is ramified by a great number of irregular vertical 





BEEHIVE COKE 


89 


fissuies, thus giving it a long columnar structure, in which the very irregular 
columns extend from the top to the bottom of the cake. This structure 
affords a second means by which beehive coke can be distinguished fro m 
by-product. 



Fio. 15. Ideal Section of Beehive Coke Oven Showing Watering Machine 

in Use and Structure of Coke. 


Watering and Drawing the Coke: As soon as the volatile matter 
has ceased to be evolved, as indicated by a subsidence of the smoke at 
the “trunnel head” and a decided shortening of the candle flames on the 
surface of the coke, the coke should be drawn. In good practice, the charge 
will be so regulated that this point is reached near the coking time assigned, 
and the ovens will be drawn on a schedule. If any circumstances delay 
the drawing, the doors of the ovens are sealed tight with clay, and the draft 
at the “trunnel head” is reduced. However, it is very important that the 
ovens be drawn on schedule, as a delay results in burning some coke and 
in cooling the oven, so that it will not coke the next charge in the period 
assigned. At the end of the coking time, then, the brick work closing the 
door is torn out, and the coke is watered out. At Continental this watering 
is accomplished by a self propelled spraying device. It consists of a tube 
or pipe a few inches shorter than the diameter of the oven, pivoted at the 
center to a feed pipe and perforated by two rows of holes on opposite sides, 
starting from the center. The holes are arranged to throw jets of water 
horizontally, which causes the pipe to revolve. Where this device is not 




















































90 


FUELS 


provided, the ovens are watered by spraying with a pipe on the end of a 
hose in the hands of a laborer, who directs a stream of water through the 
door of the oven. For drawing the coke, a Covington coke drawing machine 
is employed at this plant. It is provided with a long arm fitted with a 
head, flat on the bottom, but inclined on the top, and a pair of hinged ears, 
or drawing lugs. Upon being pushed by motor into the oven, the head 
moves in advance of the drawing lugs, which lie flat, and raises the coke 
from the bottom of the oven. Upon the return, the lugs engage this loosened 
coke and force it through the door in advance of the head. Here the coke 
falls upon a belt conveyor running parallel to the ovens, and is carried to 
the loading conveyor, which is inclined and extends at right angles to the 
row of ovens. At the top of the loading conveyor the coke falls upon a 
stationary screen, to separate the breeze, then slides down a chute into 
a railroad car, and is ready for shipment. It is impossible to remove all 
the coke with the machine, and what remains must be drawn by hand, so 
while the machine moves forward to the next oven, a laborer cleans out 
the oven with a long handled scraper, drawing the coke out upon the con¬ 
veyor of the machine, which is more than long enough to span the distance 
between the doors of two adjacent ovens. In straight hand drawing, the 
coke is drawn out into the yard and forked into barrows, which are used 
to wheel the coke into railroad cars. 

Longitudinal Ovens: In order to adapt better the beehive oven to 
the use of mechanical devices and effect a saving in labor, there appeared 
in 1906 a modified form of the old Belgian oven, known as the Mitchell 
oven. The essential features of this type of oven are a long narrow chamber, 
rectangular in shape, with a flat tile bottom, an arched roof sloping towards 
the ends, a “trunnel head” in the center of the roof, and two doors, one at 
each end, which extend over the entire width and height of the oven ends. 
These ovens are built side by side in blocks or batteries, and are charged, 
controlled and watered like beehive ovens. The coke is pushed out of the 
oven by a mechanical pusher upon a loading conveyor which is made to 
screen the coke and drop it directly into railroad cars. 

SECTION VIII. 

THE BY-PRODUCT PROCESS FOR MANUFACTURING COKE. 

General Features of the Process: The by-product process, being a 
true distillation process, involves the use of retort ovens. While there 
are many modifications, these ovens may be said to consist essentially of 
three main parts, namely, the coking chambers, the heating chambers, and 
the regenerative chambers—all constructed of brick. The retorts are 
rectangular in shape, varying in general from 30 to 42 feet in length, from 
6 to 10 feet in height, and from 17 to 22 inches in width, and are built in 
batteries, of from 40 to 90 ovens, in which the coking chambers alternate 
with the heating chambers. The coal is charged through openings in the 
top of -the oven, and the coke is pushed out one end by means of a power 
driven pusher acting through the other end. All watering is done outside 





BY-PRODUCT COKE 


91 


of the oven. During the coking period, the ends of the oven are closed 
by brick lined doors, while an opening in the top, connected with suitable 
pipes, provides a means for the escape of the volatile products of the coal, 
which must undergo several different treatments in order to separate the 
many valuable products. As to the combustion chambers, these consist 
of a great number of flues, in order to secure a uniform temperature through¬ 
out the entire length of the oven, and may be either of the horizontal flue 
or of the vertical flue type. While some of the older ovens employed the 
recuperative principle for pre-heating the air for combustion, modern 
practice demands the use of regenerative chambers, because the heat is 
better conserved and less gas is required thereby to operate the oven. 
In the arrangement of these regenerators, two plans have been employed 
with about equally good results. By the first plan the regenerative 
chambers, two in number, are placed longitudinally beneath a whole battery 
of ovens, but in the second plan a small regenerator is placed under each 
end of each oven. The latter has been employed in the most up-to-date 
plants, because each oven is thus made more nearly an independent unit, 
and the operation of the whole battery is not liable to be influenced by one 
or two ovens that may be shut down for repairs or other reasons. 

Advantages of the By=product Process: From the brief description 
given above, it will be surmised that the initial cost of a by-product 
installation is very great. Nevertheless, owing to its many advantages, 
the method is rapidly becoming the leading process for the production of 
coke in this country. These advantages as stated by Mr. Carl A. Meissner 
are as follows: 

1. “The by-product coke plant can be constructed at or near the blast 

furnaces which are to consume its coke, and thus be under the 
same management. 

2. It is practicable to ship to it coking coals from any section within 

a radius of a favorable freight rate. 

3. Many coals not suitable for coking in beehive ovens become 

available for by-product ovens by mixing with other coals and 
are so used to make a first-class blast furnace coke. 

4. Coking coals in by-product ovens permit of the full recovery and 

use of the very valuable by-products and the gas. 

5. The cost of making by-product coke at the iron and steel works 

is considerably less than the cost of making beehive coke at the 
coal mines and transporting the coke to blast furnaces, especially 
when located some distance away from the beehive district. 

G. The profits thus obtained give a substantial return on the invest¬ 
ment in by-product coke plants, large though such investment 
may at first appear.” 

The Plant of the Clairton By=product Coke Company is located 
at Clairton, Pa., in close proximity to the Clairton Steel Works and Fur¬ 
naces. This plant is the largest of its kind in the world. It consists 




92 


FUELS 



Fig. 16. Koppers By-Product Coke Ovens. 

Illustrating Cross Section of Battery. 

Coking Chamber. 2. Heating Chamber. 3. Horizontal Flue. 4. Opening to Top. 5. Regenerative Chambers. 


































































































































































































































































BY-PRODUCT COKE 


93 


of two units, the first of which was completed in the Spring of 1918. Each 
unit consists of 768 ovens. The ovens are constructed in groups, or 
batteries, of 64 ovens each, and in each unit they are arranged in two 
parallel rows of six batteries each. As each oven has a capacity of 13.3 
net tons of coal, more than 25000 tons of coal per day are required to 
supply these two units when coking on a 19-hour schedule. From 
this coal there are produced in the neighborhood of 16,700 net tons of fur¬ 
nace coke; 500 net tons of domestic coke; 1,500 net tons of breeze and 
dust, which is used to generate steam for the plant; 275,000,000 cubic feet 
of gas (average thermal value 565 B. t. u.), 57 per cent, of which is sur¬ 
plus not needed for heating the coke ovens at the plant and therefore 
available as fuel gas for the mills; 285,000 gallons of tar; 650,000 pounds 
of ammonium sulphate; 68,000 gallons of motor benzol, or 50,000 gallons 
C. P. benzol, 11,500 gallons C. P. toluol and 10,500 gallons refined solvent 
naphthas; and 10,000 pounds of crude naphthalene. The coal for the works 
is obtained from the mines of the H. C. Frick Coke Company in the lower 
Connellsville Field, and is known commercially as Klondike coal. These 
mines are located near the Monongahela River, and the coal is transported 
from the mines to the coke works by water, for which purpose more than 180 
barges of 1,000 tons capacity each and ten steamers are employed. 

Construction of the Ovens: The ovens of this plant are known as 
the Koppers 500 cubic feet by-product oven. All parts of these ovens are 
constructed almost entirely of the best grade of silica brick. To give the 
coking chamber a volume of 500 cubic feet, each oven inside has a length 
of 37 feet from face to face of the doors, a height of 9 feet 10 inches from floor 
to roof, and a width that tapers from 17 inches at the pusher end to 19J4 
inches at the discharge end. Four “trunnel heads’’ in the top provide 
means for admitting the charge, while a separate opening at one end provides 
an outlet for volatile matter. The oven is of the vertical flue type with 
individual regenerative chambers. The heating chamber is composed of 
a total of thirty vertical flues, which rise from the bottom of the chamber, 
where they are provided with openings to the regenerative chambers and 
to the gas mains, to a large horizontal cross-over flue on a level a little below 
the top of the coking chamber. A dividingwall near the middle of the oven 
separates this chamber, except the cross-over flue, into two parts with 
sixteen vertical flues on the narrower end of the oven and fourteen on the 
wider end. Each end, approximately each half, of the oven may thus be heated 
alternately, and in practice the reversals are made, automatically every half 
hour for each battery of sixty-four ovens, by means of a reversing motor con¬ 
trolled by an electrical clock attachment. Two large underground flues, 
one on each side, extending along in front of and parallel to the battery and 
connected to the checker chambers by means of cast iron goose necks, furnish 
means for the escape of the products of combustion. These flues lead to 
a stack, which is located at one end of the battery and is 200 feet high in 
order to furnish the draft necessary to draw the gases through their tortuous 
course. An idea of the magnitude of the structure may be gained from the 



94 


FUELS 


fact that a single battery of these ovens contains the equivalent of about 
2,500,000 nine inch brick. 



_ S*zzzzzzzzzz?zzzzza'\ 


A < .' . ' 


Fig. 17. Koppers Standard Coke Oven. Cross Section of Coking and Combustion Chambers. 

1. Coking Chamber. 2. Combustion Flue with gas nozzle at bottom. 3. Horizontal Flue. 4. Opening through top. 

5.Checker Chamber and Flue. 6. Flues under checkers. 7. Flue to stack. 8. Cast iron connection from checkers to stack flue. 
9. Gas main. 10. Gun brick. 11. “Trunnel Head”, and Outlet for Volatile Matter on the right. 






























































































































































































































































































BY-PRODUCT COKE 


95 




Heating the Ovens: This construction may be further explained by 
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96 


FUELS 


for combustion is admitted to the checker chamber through a capped 
opening on the goose neck leading to the stack flue. From the top of the 
regenerators it is delivered through individual openings into each of the 
fourteen or sixteen vertical flues on the side of the oven where the combustion 
is to occur. Likewise, the gas for combustion, which is conducted from the 
gas main into a fire brick gas duct located below the vertical flues, is admitted 
through individual fire brick nozzles to each of the vertical flues, about 
10 inches below the air openings. Thus, the gas and air meet in the flues, 
combustion occurs, and the hot waste gases are carried over to the opposite 
side of the battery by the horizontal flues, then down the vertical flues, 
through the checker work, out through the goose neck and into the large 
flue that leads to the stack. In order to secure uniform heating of the 
oven at all times, individual regulation of the draft in each vertical flue 
is provided by means of a brick that may be pushed out over the top of 
the flue to reduce the size of the opening. In the top of the oven an opening, 
which is closed by a plug except as occasion demands it to be opened, pro¬ 
vides access to the sliding brick and also to the gas nozzle in case it is 
desired to change the amount of gas admitted. The total amount of air 
admitted to each oven is controlled by an adjustable valve at an opening 
in the goose neck. 

fe 

Drying and Heating New Ovens: Great care is required in preparing 
new ovens for their first charge. This preparation is carried out in two 
stages, namely, a drying and a heating period, in both of which the tem¬ 
perature of the ovens must be raised very slowly and uniformly, in order 
to avoid uneven expansion and consequent cracking of the brick work. 
Both operations are carried out by building fires in the coking chambers, 
which are temporarily provided at each end and near the tops with a number 
of small holes, less than two inches in diameter, that open into the combustion 
chambers and thus furnish a passage for the products of combustion through 
the flues and checkers to the stack. The drying operation is effected with 
wood fires and occupies a period of two weeks or longer, during which time 
the temperature of the ovens is raised to 250 °F. Coal fires are then 
substituted for the wood, and the heating period is begun. About four 
weeks are required for this heating, during which time the temperature 
of the ovens is raised at the rate of about 25 °F. each day. The ovens 
are then heated rapidly up to the coking temperature of 1700° F or more. 
When available, gas may be substituted for the wood and coal for heating 
the ovens. 

Operation of the Ovens: Upon reaching the docks at the coke plant, 
of which there are two to a unit, the coal is unloaded from the barges by 
means of grab buckets (5 ton) which drop it into the hoppers of crushers. 
These hoppers are provided with 21^-inch cataract screens, so that only that 
portion of the coal that is too coarse for coking passes to the crushers. 
Here this coarse coal is crushed to lumps 2U? inches, or smaller, in size, and 
falls, together with that from the cataract screen, upon a conveyor belt 
and is carried to the eight bunkers, each of which is located above and 



BY-PRODUCT COKE 


• 97 


between two batteries of ovens. These bunkers have a capacity of 4,000 
tons each, so that four bunkers contain, when filled, enough coal to supply 



one unit for 24 hours. From the bunkers 
the coal is charged into the ovens by 
means of larry cars that travel length¬ 
wise of the batteries and on top of the 
ovens. Each larry holds a single oven 
charge of 13.3 tons, and is so constructed 
that the coal is measured both by vol¬ 
ume and by weight. From the larry, 
which has the form of four large funnels, 
the charge is dropped into the oven 
through the four “trunnel heads,’’ the 
doors of the oven having been previously 
set in place and luted with a mixture of 
loam or clay and coke dust. A recipro¬ 
cating levelling bar, carried on the pushing 
machine, is then inserted through a small 
opening at the top of the door on the 
narrower end of the oven, and the peaks 
of coal are levelled to a uniform depth 
of 9 feet, thus filling the oven to within 10 
inches of the top. Finally, all openings 
to the oven are closed and sealed, the 
valve or damper to the gas collecting 
main is opened, and the coking process, 
which lasts for a period of 19 hours or 
less, begins. The heat for coking being 
supplied from the heating chamber by 
conduction through the walls of the oven, 
coking proceeds from both sides of the 
oven toward the middle, with the result 
that a marked plane of cleavage is 
produced vertically down the center of 
the whole charge. This fact gives to 
the coke a short, block-like structure 
that distinguishes it from beehive coke, 
which, as previously noted, has a long 
columnar structure. At the end of the 
coking period the doors of the oven are 
moved to one side by mechanical devices 
for the purpose, and the coke is pushed out of the oven from the narrower end 
by means of a ram mounted upon the pusher previously mentioned. The 
coke falls into a side-dump hopper car, is carried therein to a quenching, or 
watering house, of which there is one at each end of a row of batteries, 
is there watered by an overhead spray until well blackened, but still hot 


Fig. 19. Ideal Section of the 
By-product Coke Oven Showing 
Structure of Coke. 





























FUELS 


98 ' 


enough to dry itself, and is then discharged into an inclined dock or bin. 
Here it is allowed to become dry and to cool somewhat, after which period 
it is permitted to fall upon a large belt conveyor and is carried up an incline 
to the screening house. The coke then falls upon an incline screen, known 
as the adjustable Grizzley bar screen. The bars usually being adjusted to 
give a 3^2 inch opening at the top and a M inch opening at the bottom, the 
furnace coke is separated from the breeze and dust and drops into a railroad 
car placed ready to receive it. The material that passes this screen may 
be further divided by rotary screens into dust and domestic coke, which is 
also loaded directly into cars. At this plant all the dust is used under 
boilers to generate steam for use at the plant. The volatile products from 
the coal pass out of the oven and are conducted through pipes to the by¬ 
product plants, of which there are two, one for each unit. 


SECTION IX. 

THE BY-PRODUCT PLANT. 

The Volatile Matter of Coal is a very complex mixture. It may be 
roughly divided into three classes of substances, based on their state at 
ordinary temperatures; namely, the fixed gases, or those substances that 
are gases at ordinary temperatures, the liquids, and the solids. The fixed 
gases are hydrogen, H 2 ; methane, CH 4 , also known as marsh gas; ethane, 
C 2 H 6 ; propane, C 3 H 8 ; butane, C 4 H 10 ; ethylene, C 2 H 4 ; small amounts of 
propylene, C 3 H 6 ; butylene, C 4 H 8 ; acetylene, C 2 H 2 ; carbon dioxide, C0 2 ; 
carbon monoxide, CO; hydrogen sulphide, H 2 S; nitrogen, N 2 ; oxygen, 0 2 ; 
and ammonia, NH 3 . The vapors that are liquid at ordinary temperatures 
are benzene, C 0 H 6 ; toluene, C 6 H 5 CH 3 ; xylene, C 6 H 4 (CH 3 ) 2 ; carbon disul¬ 
phide CS 2 ; and aqueous vapors. Among the vapors that are solid at ordinary 
temperatures, are naphthalene, Ci 0 H 8 ; phenol, also known as carbolic acid, 
CeH 5 OH; anthracene, Ci 4 Hi 0 ; and many others, all of which, together with 
heavy pitch-like substances, soot carbon, and small amounts of many of the 
more volatile liquid compounds cited above, enter into and make up the tar. 

Gas Mains and Coolers: All these substances pass out of the ovens 
through up-takes at their narrower ends and into the U-shaped gas collecting 
main that extends above and parallel to a battery. The gases and vapors 
enter this collecting main at a temperature of about 400 °C, and under 
a uniform suction of about .078 inch (2 mm.) of water, which is kept 
constant by means of a Northwestern gage governor and valve. From 
the collecting main the gas is conducted by two pipes to a large main, 
known as the suction main, which serves as a common main for one half of 
a row of six batteries. This suction main leads to the primary coolers. In 
passing through these mains, the temperature of the gases drops to about 
75°C, at the inlet to the primary coolers. This reduction in temperature 
causes much of the heavy tar vapors to condense in the mains, and it is 
found necessary to maintain a heavy stream of new flushing tar (composed 





TAR AND AMMONIA 


99 


of tar, 50%, and ammonia liquor, 50%), flowing through the collecting 
mains to keep them clear of pitch and carbon stoppages. The require¬ 
ments for this flushing tar amount to approximately 450 gallons of tar and 
weak liquor to be circulated through the gas mains for each ton of coal 
carbonized in the ovens. The primary coolers are large rectangular tanks 
provided with tubes through which water circulates, while the gas, in its 
passage through the cooling chamber, is brought into intimate contact 
with these pipes. The gas leaves these coolers at a temperature of about 
32 C. Ihe cooling of the gas in its travel from the ovens through the gas 
mains and primary coolers results in the condensation of about 95 per cent 
of all the tar and water vapor. The condensation takes place about as 
follows: 50 per cent in the collecting mains and cross-over mains, 35 per 
cent in the suction main, and 10 per cent in the primary coolers. The con¬ 
densing vapors carry with them all of the fixed ammonia in the gas which 
amounts to about 15 per cent, of the total ammonia. 

Separation of the Tar and Ammonia Liquor: These condensed 
liquids, composed of about 70% tar and 30% ammonia liquor, are conducted 
through pipes to two large tanks known as the hot drain tanks, or tar w r ells, 
whence a small portion is pumped back into the gas mains as flushing tar 
and the remainder to two separating tanks. In these tanks the tar and 
liquor, the former of which has a specific gravity varying from 1.15 to 
1.17 at 15 °C while the latter is little, if any, heavier than water, are allowed 
to separate by gravity, when the liquor is drained off into storage 
tanks and the tar is pumped also into storage tanks. From these 
storage tanks the tar, which is composed of water, 2%, pitch, 65%, 
and heavy oil, 33%, and has a heating value of about 16,500 R. t. u. 
per lb., is withdrawn to a small loading tank from which'it is loaded by 
gravity into tank cars as it is required for shipment; but since the semi- 
direct process for the recovery of ammonia is employed, the ammonia 
liquor, containing about 1.1% of ammonia, is pumped to ammonia stills. 
Here, the liquor is brought into contact with steam heated lime water, 
which liberates the ammonia. This ammonia gas is then conducted through 
cast iron pipes back to certain points in the gas mains, where it is disposed 
of in a manner to be described later. If desired, this ammonia gas may be 
conducted into water to produce concentrated ammonia liquor. For oper¬ 
ating these stills exhaust steam from various engines in the plant is used. 

Compressors and Tar Extractors: After the gas leaves the primary 
coolers, it enters a number of positive exhausters (Connersville Exhausters) 
which produce a suction of 15 inches of water on the entering side and 
compress the gas to a pressure equivalent to 50 inches of water on the 
discharge side. This pressure is required in order to force the gas through 
the apparatus succeeding, the first of which are the P. and A. (Pelouze 
and Audouin) tar extractors. In each of these extractors the gas stream, 
by means of a perforated plate, is broken up into innumerable small jets 
which impinge upon the cold surface of a plate immediately behind the 


> > ) 




100 


FUELS 


perforated plate. The impact causes the very fine particles of tar to collect 
on the impact plate, and the tar, thus accumulating, runs off the plate and 
out of the apparatus through a sealed overflow at the bottom. In these 
apparatus it is necessary to maintain a constant differential pressure of 
about 8 inches of water, and since the holes in the perforated plate tend 
to become closed by the more viscous of the tarry substances, thus causing 
an increase of the pressure, special means must be employed to overcome 
this tendency. At this plant the desired result is accomplished by lower¬ 
ing the tar level in the bottom of the apparatus, thus exposing more holes 
as those in use become clogged. The tar level is controlled by means of 
a pressure gauge and automatic regulator attached to the gate valve 
through which the tar passes in flowing out of the apparatus. The tar 
extracted by this machine amounts to about 5% of the total tar originally 
carried by the gas. 

Recovery of Ammonia: The temperature of the gas, now about 38°C., 
having been raised about 6°C. by compression in the exhausters, is brought 
to about 66°C. by being forced through preheaters, which are cylindrical 
steel tanks containing steam coils. This preheating is necessary to 
prevent the accumulation of water in the saturators and to accelerate the 
reaction, between the ammonia and the dilute sulphuric acid, that occurs 
in them. These saturators, of which there are ten to a unit, are large 
lead lined steel pots containing a 5% solution of sulphuric acid, through 
which the gas is forced in tiny bubbles. This gas, it is to be noted, 
contains all the ammonia recovered from the coal, for that which 
was liberated in the ammonia liquor stills, previously described, has 
been introduced into the gas mains just after the latter leaves the 
preheaters. In this way all the ammonia given off by the coal in coking 
is brought into direct contact with the dilute acid, with which it immedi¬ 
ately reacts to form ammonium sulphate, (NH 4 )2 S0 4 . This salt dissolves 
in the water with which the acid was diluted, but, when the baths become 
saturated, it is precipitated and settles to the bottom, where it is forced' 
through syphon ejectors by means of compressed air to elevated draining 
tables, also lead lined. From the draining tables, the salt is periodically 
removed, placed in centrifugal dryers, and whizzed for fifteen minutes, 
which process removes nearly all the water, the salt retaining about 
2 . 0 % of its own weight of moisture. The mother liquor derived from the 
drying operations, as well as the wash water used to free the crystals of the 
slightly acid mother liquor, flows back into the saturators, while the salt 
is scraped off the copper screen plates of the centrifugal machines with 
wooden paddles and delivered through a chutt, to a belt conveyor, which 
carries it to a final dryer, where the moisture content, by means of hot 
gases, may be reduced to .25% or less. The final drying prevents caking, 
so that the salt will remain in a finely divided state for indefinite periods. 
From the final dryer the salt falls into a pit, from which it is removed with 
grab buckets to a storage pile, to be shipped later as required. 




BENZOL PLANT 


101 


Debenzolating the Gas: In bubbling through the liquid in the 
saturator, the gas tends to carry a little of the acid along with it. Hence, 
from the saturator the gas passes into an acid separator. Its temperature 
here is about 54°C. which is much too high for the complete separation 
of the benzene and its homologues. Therefore, the gas is put through finaf 
coolers where its temperature is lowered to 30°C. These coolers are tall- 
steel towers, about 100 feet in height. In them the gas is brought into- 
direct contact with cold water, which is introduced at the top, while the 
gas enters at the bottom and leaves at the top. From these coolers the 
gas is forced through three benzol, or oil, scrubbers in series. Like the 
coolers, these scrubbers are large steel towers, in which the principle of 
counter currents is employed throughout. They are filled with a kind of 
checker work of wooden slats. A product from the refining of petroleum, (or of 
tar), known as straw oil or wash oil, with a distilling temperature ranging from 
270 to 370°C., is sprayed into the top of the washers, where it trickles down 
over the wooden checker work and is thus brought into intimate contact 
with the ascending current of gases. The oil absorbs the benzene, toluene, 
xylene, naphtha and naphthalene, becoming saturated to the extent of 
about 3%, and removing 92% or more of the total amount of these products 
in the gas. The entire removal of the naphthalene at this point is of great 
importance, because, if any remains in the gas, it crystallizes out and clogs 
the gas lines. From the scrubbers, the oil carrying the benzene, toluene, 
etc., is pumped to the benzol plant, which serves both units of the plant, 
while the gas, now freed from all except its fixed gases, is divided, half 
being sent to the fuel lines to heat up the ovens and half to the booster 
station, where it is compressed by steam turbo-blowers and delivered to 
the mills as surplus gas. The loss in heating power of the gas from a given 
quantity of coal, due to the removal of the by-products, amounts to about 
5.8%. 

SECTION X. 

THE BENZOL PLANT. 

Light Oil: At the benzol plant the wash oil, carrying in solution the 
benzene-, naphthalene, and their homologues, is first delivered to the wash 
oil, or separating, stills. In order to conserve as much heat as possible, 
the inflowing wash oil is made to serve as a condensing liquid for the 
vapors from the still. After leaving the condensers, or heat exchangers, 
the oil passes to preheaters, or superheaters, in which its temperature is 
raised to about 145°C. and much of the benzol is vaporized. The oil then 
passes to the stills, where it comes into direct contact with steam which 
drives off the higher boiling oils and naphthalene. Since the wash oil has 
a much higher boiling point than the hydrocarbons it is desired to recover, 
only a small portion of it escapes from the stills. The vapors from the 
stills, passing into the condensers, or heat exchangers, are cooled and con¬ 
dense to form a liquid, known as “light oil,” which flows from the bottom 
of the condensers into storage tanks. The wash oil, which is not vapor¬ 
ized, flows from the bottom of the stills and is conducted to heat exchang- 








102 


FUELS 


ers, and then to water coolers where its temperature is lowered to 30°C. 
From these coolers it is pumped back to the oil scrubbers, and can be used 
repeatedly. However, there is a daily loss of approximately 2%. 

Composition of the Light Oil: The light oil is pumped from the 
storage tank to the crude still. The composition of a light oil is approx¬ 
imately as follows: 

Light Runnings (benzol and carbon bisulphide). 1.00% 


Pure Benzol.57.00% 

Pure Toluol.14.50% 

No. 1 Refined Solvent Naphtha. 4.50% 

No. 2 Crude Heavy Solvent Naphtha. . .. 1.50% 

Crude Naphthalene.40% by weight. 

Wash Oil.12.00% 


Construction and Principles of the Still: The crude still consists 
of three sections. The lowest section is a horizontal cylinder provided 
with steam coils, and has a capacity of 20,000 gallons; the second part, 
called the fractionating column, is a vertical column mounted upon this 
cylinder and composed of thirty-one bell sections for scrubbing the vapors 
as they pass upward; the third part, mounted on top of the column and 
called the dephlegmator, is a short horizontal cylinder, that contains a 
number of water cooled pipes and acts as a partial condenser. The separa¬ 
tion of light oil into its component oils is effected by taking advantage of their 
different boiling points. As the temperature of the light oil is raised and ap¬ 
proaches the boiling point of the first runnings, this liquid is vaporized and 
passes up through the column; a portion of the other oils with higher boiling 
points is also vaporized, but is condensed before reaching the top of the col¬ 
umn. There are thus two movements in the fractionating column and de¬ 
phlegmator, the vapors going upward and the condensed oils flowing down¬ 
ward into the still. The vapors are thus forced to pass through the return 
oils which aid in condensing the vaporized oils of higher boiling points and 
permit only the lighter vaporized oils to reach the top of the dephlegmator, 
where they are condensed and flow from the still through a manifold into 
the storage tanks. As the temperature of the still is further raised, the 
benzol, toluol, etc., is successively vaporized and condensed, and flows from 
the still. However, it is impossible to separate absolutely, the benzol from 
the toluol, since, before the benzol is completely driven over, some toluol will 
be carried along with it. It is likewise impossible to separate absolutely one 
from another the other constituent oils. Hence, it is only aimed to separate 
roughly the light oil into what are termed fractions. These fractions, desig¬ 
nated in the order in which they are made, are as follows: Light Runnings, 
Crude 90% Benzol, Crude 90% Toluol, Crude Light Solvent Naphtha, Crude 
Heavy Solvent Naphtha and Still Residue. Each fraction is stored in a 
separate tank. 

Operation of the Crude Still: The details of the operation of the 
crude still are as follows: 20,000 gallons of light oil are charged. The 










BENZOL PLANT 


103 


temperature is gradually raised, and approximately 1,600 gallons of oil are 
vaporized and condensed. This product, known as the light runnings and 
consisting of benzol containing approximately 3% carbon bisulphide, is 
conducted into the light runnings storage tank. The next product is the 
90% benzol. The still is continued on this fraction until a test shows 
30% by volume will distill over at 100°C. Ninety per cent, toluol is then 
collected until a test shows that 10% will distill over at 130°C. The next 
product is the light solvent naphtha which is collected until the flow of 
oil is very small, at which point, and continuing throughout the operation, 
the still is maintained under partial vacuum. The oil in this fraction is 
collected until 10% will distill over at 160°C., when heavy solvent naphtha 
is produced until a test shows that 90% will distill over at 205°C. The 
residue in the still, consisting of wash oil and naphthalene, is drained into 
the naphthalene pans, where, upon cooling, the naphthalene separates: 
as a solid. The wash oil is removed by a centrifugal machine, and 
the naphthalene is washed with hot water. It is sold as crude naphthalene, 
or refined and sold as C. P. naphthalene. 

Washing the Products of the Crude Stills: Before the products of 
the crude still are further treated for the separation of their component 
oils, they are pumped to the washer and there agitated with sulphuric acid. 
The object of this treatment is to free the oils from unsaturated hydrocarbon 
compounds, paraffins and other impurities. These substances are acted 
upon and polymerized by the acid, to form substances that have very high boil¬ 
ing points. Some of these are insoluble in the oils and will settle out with 
the acid, forming a sludge. Several thousand gallons of oil are transferred 
to the washer and 66° Baurne sulphuric acid is added, the proportions being 
about 920 pounds of acid to 5,000 gallons oil. The contents of the washer 
are agitated for twenty minutes and allowed to stand for fifteen minutes, 
when the sludge settles to the bottom and is drawn off. This acid sludge is 
then heated in special pots with live steam, and the acid thus separated from 
the carbon aceous matter, when it is used in the saturators to produce ammon¬ 
ium sulphate. For the purest product the oil is then washed an additional 
number of times in the same manner. After the use of the acid, the oil 
is washed with 10% caustic soda solution until the last trace of acid is 
neutralized. The oil is then transferred to the pure still. 

The Pure Stills: The construction and operation of the pure still is 
practically identical to that of the crude still. However, while the fractions 
of the latter consist of a mixture of oils, the pure still is operated so that 
one or more fractions maybe pure compounds, as is shown by the following 
data: 

Still Charge—17,676 Gals. Washed 90% Benzol. 
Fraction. Time Gals. Product. 

1 12% hrs. 1440 R. R. (Rerun) Benzol—Benzol containing 

Carbon Bi-sulphide. 

2 31 “ 10950 C. P. Benzol. 





104 


FUELS 


Fraction. Time Gals. Product. 

3 2% hrs. 790 R. R. (Rerun) Benzol—Greater portion 

Benzol, part Toluol. 

Residue 4496 . Principally Toluol. 

Fraction 2, being pure benzol, is not further treated, and is ready for the 
market. The rerun (R. R.) benzol fraction, 1 and 3, and the residue are 
stored in separate tanks. When a sufficient quantity of a R. R. fraction 
has accumulated, the pure still can be charged with it and a C. P. 
(chemically pure) product obtained, as is shown by the following data: 

Still Charge—18,200 Gals. 


Fraction. 

Time 

Gals. 

R. R. Benzol. 

Product. 

1 

16% hrs. 

2550 

R. R. Benzol—containing Carbon Bisulphide. 

2 

39 

10900 

C. P. Benzol. 

3 

10 

1750 

R. R. Benzol—Greater portion Benzol, part 

4 

5 

650 

Toluol. 

R. R. Toluol—Part Benzol, greater portion 

5 

6 X “ 

1300 

Toluol. 

C. P. Toluol. 

Residue 

1050 

Toluol and Solvent Naphtha. 

Fraction 2 and 5 being 

C. P., are ready for the market, the other 


fractions are stored and, when a sufficient amount is collected, are distilled 
like the R. R. Benzol charge just described. It is not essential that the 
pure still be charged with a straight R. R., or 90% product, as a mixture 
of the two-is often distilled as follows: 

Still Charge—6800 Gals. 90% Washed Toluol. 

10150 “ R. R. Toluol. 


Fraction. 

Time. 

Gals. 

Product. 



1 

15% hrs. 

1610 

R. R. Benzol—greater portion 

Benzol, 

part 




Toluol. 



.2 

29 

5130 

R. R. Toluol—greater portion 

Toluol, 

part 




Benzol. 



3 

24 

6950 

C. P. Toluol. 



4 

6% • 

400 

R. R. Toluol—greater portion 

Toluol, 

part 




Naphtha. 





2860 

Residue—Toluol and Naphtha. 




It is thus apparent that the light oil will eventually be completely 
worked up into its pure product. There is one exception, however, in that 
the light runnings containing the carbon bisulphide cannot be separated by 
fractional distillation. The crude carbon bisulphide benzol is the first 
1600 gallons that come over , in the crude still. This is placed in a 
separate tank, into which the forerunnings, or carbon bisulphide benzol, 
from the pure still is also collected. When 20,000 gallons of this product, 
containing approximately 3% carbon bisulphide, is collected, it is placed 





BENZOL, TOLUOL, NAPHTHA 


105 


in the 90% crude still. The first 4000 gallons condensed is benzol 
containing 10 % carbon bisulphide, the remaining portion is 90% benzol, 
which is transferred to the crude 90% benzol tank. Only a restricted 
market has so far been found for the 10 % carbon bisulphide benzol. 


SECTION XI. 

SOME PROPERTIES AND USES OF THE RAW 
BY-PRODUCTS FROM THE COKE WORKS. 


Characteristics of Benzol, Toluol and Naphtha: While the names 
benzol, toluol, xylol and naphtha are those commonly applied in commerce, 
chemical names used to designate corresponding pure compounds are 
benzene, toluene, xylene, cumene, etc. Naphtha is a mixture of several 
compounds, including xylene, cumene and others, so it has no chemical 
name. As previously indicated, these compounds are members of the 
aromatic, or benzene, series of hydrocarbons represented by the general 

formula C n H 2 n_6. The empirical formulas for benzene, CeH 6 , and toluene, 

C 7 H 8 , represent individual compounds, but these formulas for xylene, 
C 8 Hio, and cumene, C 9 H 12 , represent series of isomeric compounds, which, 
though they are members of the same series and may have the same formula, 
differ widely in properties. Thus the formula CsHio, may represent 


CHs 

1 

C 

/ \ 

orthoxylene H-C C-CHa; 

II I 

H-C C-H 
\ = 

C 

1 

H 


CHs 

1 

C 

/ \ 

metaxylene H-C C-H; 

H-C C-CHs 

\ ^ 

C 

1 

H 


paraxylene, 


CHs 

b 


/ % 

H-C C-H; 


H-C C-H 

\ S 


C 

ClHs 


or ethylbenzene, 


C2H5 

1 

C 

/ \ 

H-C C-H. 

II I 

H-C C-H 

\ S 

C 

h 


The chief physical properties of the first and more important members 
of the series are given in the following table, which will also give some 
idea of the method of naming the compounds: 



106 


FUELS 


Table 13. Some Members of the Benzene Series and 
Their Physical Properties. 


FORMULAS 

NAME 

State at 
Ordinary 
Temperature 

Melting or 
Freezing 
Point °C. 

Boiling 

Point 

°C. 

Specific 

Empirica 

Rational 

Gravity 

C 6 H 6 .. 

C 7 H 8 .. 

CsHe 

Benzene. 

Clear Liquid 

+5.4 

80.4 

.884+1 

C 0 H 5 . CH 3 . 

Toluene or 


w 


Methyl- 
benzene. . . . 

( ( * < 

—92.4 

110.3 

00 

C 8 Hio . 

C 6 H 4 . (CH3)2 • . . . 

Ortho xylene 
or Ortho¬ 
dimethyl- 
benzene. . . . 

Meta-xylene 
or dimethyl- 
benzene. . . . 

Para-xylene 
or dimethyl- 
benzene. . . . 

«• «« 

—28 

142.0 

r o°] 

.893 <-> 

\ 4 °f 



* t < < 

—54.8 

139.1 

/ o 1 O 
lO 

N | 

00 



* • ( c 

+ 13° 

138.0 

/ °°\ 
880< - V 




\ 4 of 


C 6 H 5 . (C 2 H 5 ) .... 

C 6 H 3 . (CH3)3- 

Ethylbenzene. 

Hemimelli- 
thene or v— 
Tri methyl- 
benzene. . . . 
Pseudocu- 

«• <1 


136 0 

.883+1 

C 9 H 12 . 

< • it 


175.0 

\ 4 °I 



mene or 

as-Trimeth- 
ylbenzene. . 

a a 


169.5 

f °°\ 

895 < > 





1 4 °/ 

Mesitylene or 
s-trimethyl- 
benzene.... 




a • • 


165.0 

/i5°\ 
,865\ — > 






1 4 °f 


C 6 H 5 . C 3 H 7 . 

Normal 







Propyl- 
benzene. . . . 

11 << 


159.0 

fl5° \ 
867s -> 





\ «•/ 



Cumene or 
Isopropyl¬ 
benzene. . . . 

l « 4 < 


153.0 

866 / 15 °l 





l 4 °/ 

C 10 Hi4 

CeH 2 - (CH3)4. ... 

Prehitene or 
Tetra- 
methyl- 
benzene.. . . 


- 




CGH 4 . CH 3 .C 3 H 7 .. 

Cymene or 
Methyliso- 
propyl- 
benzene... . 





and so on to C 25 H 4 . 4 .. 






























































BENZOL 


107 


Commercial Benzol: The term “benzol” is employed commercially in 
connection with the various mixtures of the benzene hydrocarbons. Pure 
benzene is usually marketed as “Chemically Pure”, or “C.P.,” benzol. The 
mixtures are generally designated as 90 % washed benzol, 90% crude benzol, 
80 % washed benzol, 80 % crude benzol, and so forth. The terms “washed” 
and “ crude ” denote whether or not the product has been washed with sulphuric 
acid to remove the various unsaturated compounds which are always present 
in the crude product. As a rule, most of these products are washed to a greater 
or less degree of refinement,according to the purpose for which they are required. 
The terms “90 %”or “80 %” refer to the amount of the fraction which will distil 
over up to 100 °C. The lower this percentage, the greater will be the amounts 
of toluol and solvent naphthas present in the product. The 90% washed benzol 
will contain approximately 80% benzol, 15% toluol, and 5 % of xylols and light 
solvent naphthas. 

Uses of Commercial Benzols: Benzols have been largely used as 
solvents for fats, waxes, gums, and resins. Mixed with alcohol and ammonia, 
benzols of these grades make an excellent cleanser for the removal of grease 
and paint. Its solvent action on gums and resins makes it a valuable substance 
in the manufacture of paints, varnishes, and lacs, especially of enamel, bronze 
and aluminum paints, in which a neutral gum, or resin, is used to form the 
bases. The solvent action of these grades upon rubber makes them valuable 
in the preparation of cements and insulating varnishes. They dissolve sulphur 
mono-chloride, and are hence used in the cold vulcanization of rubber. Heavy 
benzol and solvent naphtha are employed in the preparation of enamels, 
wood stains, varnishes, and waterproofing materials, such as the rubberized 
cloth known as mackintosh. Certain grades may be used as a substitute 
for turpentine in paints intended to cover resinous woods. Naphtha, in par¬ 
ticular, is important as a rubber solvent in the manufacture of rubber goods, 
and as a solvent for anthracene during the final purification of this substance 
with sulphuric acid. It is also used in the cleaning of clothing. 

Motor Benzol: A product corresponding approximately to 80% washed 
benzol makes an excellent motor fuel for automobile engines, though up until 
1919 it had not been extensively used as such in the United States. Inasmuch 
as the commercial use of pure benzol and pure toluol is comparatively limited, 
since the demand for explosives has decreased, fully 80% of all the benzol and 
toluol now produced in the United States is used as a motor fuel. For this 
purpose there is no necessity of separating the toluol from the benzol,and all 
of these two substances, together with practically all of the xylol, are combined 
in one product. This product is marketed as “Motor Benzol”. Pure benzol, 
freezing at 5.4°C., congeals readily in cold weather, but the presence of the 
toluol and xylol in motor benzol lowers this freezing point so that cars may be 
satisfactorily operated during freezing weather. Gasoline to the amount 
of about 25% mixed with this product makes a mixture suitable for the coldest 
weather. Any carburetor adapted for gasoline can be used as well for motor 
benzol, but more air, or oxygen, is required in the explosive mixture with this 


I 



Table 14. Diagram Showing Some of the Products Derived from Benzene, Their Formulas and Their Uses. 


108 


FUELS 




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PURE BENZOL 


109 


fuel than with gasoline. When properly handled, motor benzol gives from 
20% to 30% greater mileage than does gasoline. At the present time motor 
benzol is made under the following specifications: 

Color Water-white. 

Distillation Start 78° to 82 °C. 

Dry not higher than 
135 °C. 

Wash Test No 9, or better. 

Sulphur content not to exceed 0.25% . 

The wash test is made by agitating equal quantities, usually 20 cc., 
of the oil and pure sulphuric acid in a glass tube and comparing the color 
with that of numbered standards, the first of which, No. 1, is perfectly clear. 


Properties and Uses of Pure Benzol, or Benzene: The chief physical 
properties of this very interesting substance have already been given. 
Concerning its chemical properties and uses, it may be said that it is one 
of the most interesting and useful compounds known to the chemical 
profession. This fact is more fully appreciated when it is known that it 
is the base from which such drugs as phenol, hydroquinon, antipyrin and 
acetanilid; such dye stuffs as resorcinol, benzidine, aniline, and indigo; and 
such explosives as nitrobenzol and picric acid are prepared. The relations 
of benzene to these compounds is best shown briefly by means of some 
such diagram as that on the opposite page. 


To illustrate the reactions by means of which some of the more 
important compounds are derived from benzene, the following tables have 
been prepared: 


Table 15. Reactions Showing How Aniline and Benzidine Are 

Derived from Benzene. 

C 6 H 6 +HN 03 (H 2 S 04 )=C 6 H 5 NO 2 +H 2 o (H 2 SO 4 ) 

Nitro Benzene. 

CnH^N 

2C 6 H 5 N02+4SnCl2+4KOH= C6 J H ^-l-2SnCl4+2H20+2K2Sn03 

Nitro Benzene. Azobenzene. 


C6H5'N02+6HC1+ 3Fe=C6H5‘NH 2 + 3Fe Cl 2 + 2 H 2 O 

Nitro Benzene. Aniline. 


CeH5 '^ + Sn Cl 2 + 2HC1 =CrIII NHo+ SnCl4 
C 6 H 5 N C 6 H 4 NH 2 

Azobenzene. Benzidine. 

Substantive Cotton Dyes. 




110 


FUELS 


Table 16. Reactions Showing How Phenol, Picric Acid and 
Resorcinol May Be Derived from Benzene. 


C 6 H 6 +H 2 S 04 =H 2 O + C6 h 5 >S0 3 

Benzene Sulphonic Acid. 


c 6 h^> s ° 3 + koh= c 6 H5> s °3 + h 2 o 

Potassium Benzene Sulphonate. 


Ce H5 >S0 3 +2KOH=K 2 so 3 +c 6 h 5 ok+h 2 o 
(H eated to fusion) Potassium Phenatei 


2 C 6 H 5 OK+H 2 SO 4 —2C 6 H 5 OH+K 2 SO 4 

Phenol. 


c 6 h 5 oh+h 2 so 4 =h 2 o+ oh . C6H ^>so 3 

Phenol. ' Para Benzene Sulphonic Acid. 


OH-Ce H4 >S ° 3+2KOH=K2S ° 3+H2 0+Ce H4 (0H)2 

Met ad i hydroxyl benzene 
or Resorcinol 
(Resorcine) 
Base of many colors. 


2C 6 H 5 0H+6HN0 3 =2C g H 2 < ( ( ^ 2)3 +3H 2 0+30 

Phenol. Picric Acid. 




TOLUENE 


111 


Uses of Toluene: One of the chief uses of toluene is found in the 
manufacture of high explosives. These are prepared by nitrating toluene. 
Both the di-nitro-toluene and the tri-nitro-toluene are used, but of these 
the latter, often referred to as T. N. T., is more important. In intensity 
of explosion it ranks below picric acid, derived from phenol, but is much 
safer to handle, because the acid has the property of reacting direct with 
metals to form picrates, which are very sensitive to shock, whereas T. N. T. 
does not form dangerous salts with metals and is not sensitive to mechanical 
shock. It is also replacing gun cotton, or nitrocellulose, in torpedoes, mines, 
etc. 


CH 3 

l 

C 

/ \ 

0 2 N-C C-NO 2 

11 1 

Its formula is represented thus: H—C C—H 

\ ^ 

C 

N0 2 

Since the molecule of T. N. T. does not contain enough oxygen for 
the complete combustion of the carbon atoms, it produces much smoke on 
burning or exploding. This defect is overcome by mixing with it some 
nitrate, preferably ammonium or lead nitrate. In addition to its use as 
an explosive, toluene is also the base from which saccharin, benzoic acid, 
many dyestuffs, and perfumes are prepared, as a glance at the accompany¬ 
ing diagram will show: (See Table 17.) 

Commercial Toluol and Solvent Naphtha: Commerical toluol, 
often spoken of as 90% toluol, is a mixture composed mainly of toluol, 
90% of which will distill at 120°C and not more than 5% at 100°C. In the 
case of solvent naphtha, 90% distills at 160°C and not over 5% at 130°. 
These mixtures are often used instead of benzol, because they evaporate 
more slowly or because they have a higher flash point. Some of the 
industries in which their use is found advantageous are the manufacture 
of automobile tires, rubber cements, artificial leather, wood stains, paint 
and varnish removers, paints (as a substitute for turpentine) and special 
inks. 



Table 17. Some Products Derived from Toluene, Their Formulas and Uses. 

TOLUENE 

CHa 


112 


FUELS 


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Explosive Dyes Food Preservative 









NAPHTHALENE 


113 


Uses of Naphthalene: Ci 0 H 8 does not belong to the benzene series, 
CnH 2 n— 6 , but is the first member of a series represented by the general 
formula CnHon— 12 , and by the structural formula H H 

i i 

C C 

II \ / % 

H-C C C-H 

i ii i 

H-C C C-H 

\ / \ = 

C * C 

i i 

H H 


It is used as an antiseptic and insecticide, and is familiar to every one 

in the form of moth balls. But its real importance lies in the fact that 

it is the base from which many dyestuffs are prepared, chief of which is 

indigo. The steps by which this important dye is derived from naphthalene 

are about asfollows: (1) Naphthalene,C i 0 H 8 ,is heated with fuming sulphuric 

acid and mercury, which acts as a catalytic agent, whereupon there is 

formed phthalic acid, CqH^COOH^, ( 2 ) which, on being heated, passes into 

CO 

phthalic anhydride, C 6 H 4 <^q >0 (3) from which phthalimide, 

CO 

C( 5 H 4 < r , n >NH, is obtained with the aid of ammonia and heat 
(4). By oxidizing phthalimide with bleaching powder, anthranilic acid, 
C 6 H 4 -NH 2 -COOH is formed, (5) which is changed by treatment with 
monochloacetic acid to phenyl-glycine-ortho-carboxylic acid, C 6 H 4 -C00H- 
NH-CH 2 -COOH, ( 6 ) By fusing this compound with caustic soda, indoxyl, 
C 2 H 4 NHCOCH 2 , is formed and is readily oxidized by the oxygen of the 
air to indigotin, C G H 4 NH.CO-C=C.CO-NH-C 0 H 4 , or indigo-blue. The 
following table will serve to show the many other dyestuffs that may be 
obtained from naphthalene: 






114 


FUELS 


Table 18. Showing Some Products Derived from Naphthalene. 

NAPHTHALENE 

C 10 H 8 __ 


Naphthionic Acid 

r* tt <^SOsH 
LioH 0 < NH2 


Phthalic Acid Nitronaphthalene ce and /3 Naphthols 

C 6 H 4 <cqq^ C10H7NO2 C10H7OH 


Dye Indigo Dye Explosives 
Stuffs Stuffs 


Dye Stuffs such as 
Biebrich scarlet, 
M a r t i 11 s and 
Naphthol yellow. 


Congo Red 

C6H4N2C10H5 

deHiNsCioHs 


Dye 


Tar: As obtained from gas works as well as from by-product coke 
plants, tar is a black, viscous, oily liquid, with a specific gravity that varies 
from 1.15 to 1.20, that from coke works having a gravity of about 1.16. 
It also varies a great deal in other respects, especially in composition. 
It is a very complex substance; the number of its compounds have 
been estimated at about 300, only some of which have been isolated in the 
laboratory and but a very few in the commercial working up of the liquid. 
In the crude state it may be used as a fuel and for road dressing, but, by 
refining, it is made to yield a great number of products of great economic 
and hygienic importance. The refining of tar forms an industry by itself, 
which requires volumes to describe in all its details. Suffice it to say, 
that the refining of tar is essentially a process of fractional distillation, 
in which it is first separated roughly into several parts, which may 
then be further rectified into purer substances as shown in the following 
diagram, which is also made to indicate the uses to which the products 
are applied. 













Table 19. Diagram Illustrative of the Refining of Tar. 




COAL TAR PRODUCTS 


115 



Fuel 

































































116 


AMMONIUM SULPHATE 


Ammonia, as concentrated ammonia liquor (NH 4 OH and H 2 0), is 
used in making anhydrous ammonia gas (NH 3 ) for refrigeration purposes 
and the aqua ammonia of commerce, used for cleaning. It is also used in 
the manufacture of baking soda and a large number of ammonium salts, 
such as ammonium chloride and ammonium nitrate. The last named salt 
is extensively used in the manufacture of explosives. By passing ammonia 
and air over heated platinum black, the former is oxidized to nitric acid, 
and large quantities of ammonium nitrate are now produced by this method. 
Ammonia is used extensively in dye works, and a considerable amount is 
consumed by chemists in analytical laboratories. 

Ammonium Sulphate, (NH 4 ) 2 S0 4 , is a white crystalline salt, very 
soluble in water and easily decomposed by heat, beginning at 140°, into 
NH 4 HS0 4 and NH 3 , and at a red heat into NH 3 , S0 2 and H 2 0. Unlike 
most ammonium salts, it cannot be sublimed. As obtained from the coke 
works, it is slightly discolored by small amounts of various impurities 
which it is impossible to exclude entirely. It is used for a number of 
purposes, including the preparation of ammonium persulphate and nitrate, 
but its great field of usefulness is exhibited as a commercial agricultural 
fertilizer. William H. Childs of the Barrett Co. who has made a careful 
study of the use of the salt for this purpose speaks thus of it: 

Use of Ammonium Sulphate as a Fertilizer: “Sulphate of ammonia 
is extensively used in ready mixed fertilizers, which is the form generally 
purchased by the American farmer. These usually contain acid phosphate 
and potash, together with sulphate of ammonia, tankage, cotton-seed meal, 
etc. Sulphate of ammonia is dry in its nature, and makes an excellent 
mixture as far as mechanical condition goes, with the added advantage 
that it does not react with the other fertilizer chemicals to cause loss of 
nitrogen or reversion of the acid phosphate, both of which points are claimed 
against nitrate of soda. The nitrogen in sulphate of ammonia is quick to 
act, is not easily leached out of the soil, and it continues its action over a 
considerable period, so that the growing plant is carried along to maturity 
without setback. Its only disadvantage is the tendency to exhaust the 
lime in the soil. While this point is apt to be urged by Agricultural Experi¬ 
ment Station men, it is really of minor importance because the actual 
amount of sulphate of ammonia in the usual fertilizer application is small, 
and its nitrogen is relatively so much more beneficial to the growth of the 
crop. The liming of the soil, which, of course, overcomes all objections, 
is urgently recommended by all Experiment Station advisers, and in large 
areas of the Eastern States is practically the foundation of profitable 
agriculture. On the other hand, in some soils, as in those of Southern 
California and parts of Texas, which tend to excess of alkali, the action 
of sulphate of ammonia is peculiarly beneficial. In some soils sulphur is 
lacking, so that the sulphur in sulphate of ammonia actually acts as a 
plant food.” 




FLUXES 


117 


CHAPTER V. 

FLUXES AND SLAGS. 

SECTION I. 

FLUXES. 

Smelting and the Functions of a Flux: Any metallurgical operation 
in which the metal sought is separated, in a state of fusion, from the 
impurities with which it may be chemically combined or physically mixed 
is called smelting. Since both these conditions with regard to impurities 
are usually present, smelting involves two processes; namely, the reduction 
of the metal from its compounds and its separation from the mechanical 
mixture. Many 0 / these impurities may be of a highly refractory nature, 
and if they were to remain unfused, they would choke up the furnace, retard 
the separation of the metal and interfere in various other ways with the 
smelting. To render such substances more easily fusible is the primary 
function of a flux. Again, some elements, being reduced almost simul¬ 
taneously with the metal, combine chemically with it, while other elements 
and some radicals, chemically combined with the metal in the raw materials, 
refuse to be separated from it, except there be present some substance for 
which they have a greater chemical affinity. To furnish a substance with 
which these elements and radicals may combine in preference to the metal 
is the second function of the flux. 

The Selection of the Proper Flux for a Given Process is, then, chiefly 
a chemical problem and requires a knowledge of the chemical composition 
of all the materials entering into the process. With this knowledge in 
hand, the selection will be governed by well known physical and chemical 
laws, chief of which is the action of acids and bases toward each other 
and the fusibility of the various compounds thus formed. In general, if 
the matter to be fluxed is basic, such as lime, magnesia and other compounds 
of base forming elements, the flux must be acid, while if the impurities be 
acid, such as silica and phosphoric acid, a basic flux will be required. In 
most ores the impurities will belong to both classes with one or the other 
class, usually the acids, predominating. In a few iron ores the two classes 
of impurities are so well balanced as to render the ores self-fluxing, or by 
proper mixing they can be made so. In order to control fusibility, a neutral 
flux is sometimes required. The cost of the flux is also to be considered, 
hence the natural deposits of greatest purity that are easy of access and in 





118 


FLUXES 


close proximity to the works are made use of. A brief discussion of the 
fluxes of greatest importance in the iron and steel industry follows: 

Acid Fluxes: Silica is the only substance that may be classed as a 
strictly acid flux. For this purpose it is available as sand, gravel and 
quartz in large quantities and in a sufficiently pure state. In blast furnace 
practice, it is customary to employ acid open hearth or Bessemer slags or 
ores of high silica content when it is desired to increase the acids in the 
furnace,as,in this way,the metallic contents of these substances are recovered. 

Alumina: Unlike silica, which is a strong acid under all conditions, 
alumina may perform either the function of an acid or a base, depending 
upon the conditions imposed. Thus, with silica, it forms aluminum silicate, 
and with a strong base, such as sodium, sodium aluminate. A marked 
peculiarity is its tendency to form, in conjunction with other bases, double 
salts with polybasic acids. As a rule, double silicates are more easily 
fused than those containing a single base. Alumina is seldom used inten¬ 
tionally as a flux, but it is present in nearly all raw material, hence unavoid¬ 
able. 

Basic Fluxes: The chief natural fluxes of this class are limestone and 
dolomite. In addition, iron and manganese oxides act as such in certain 
processes where their performing this function is uncontrollable, as is the 
case in the acid open hearth. Referring to limestone and dolomite as blast 
furnace materials, there is a difference of opinion among furnacemen as to 
their relative value as fluxes. Some hold that limestone is the better, 
while others maintain that dolomite gives as good, if not better results, 
their opinions usually being influenced by their training and by the extent 
of their experience with these materials. The presence of magnesium in 
limestone in small amounts has little effect, but as the content increases, 
it may lower the fusion point of the resultant slag by the formation of 
double salts. A high percentage (over 3%) of magnesia in blast furnace 
slag renders it undesirable for cement, but for concrete, ballast, etc., it is 
desirable, as it makes the slag harder. Aside from this objection, not 
one of much weight, the factor that governs the choice between limestone 
and dolomite is the cost per ton of available base. 

Available Base: By available base is meant the amount of basic 
substance that remains in the raw flux after the acids of its own 
content are satisfied. Referring to the analysis of limestones on a 
succeeding page, it is at once noticed that the total is not 100%. The 
substance that is missing is carbon dioxide, which constitutes 44.0% of pure 
calcium carbonate, and, being evolved as a gas, is seldom determined in 
making an analysis. Using the Bessemer stone as an example and 
remembering that the iron and phosphorus are completely reduced in the 





LIMESTONE 


119 


furnace, we have remaining Si0 2 , 3.43%; A1 2 0 8 , .86%; CaO, 51.45%; 
MgO, 1.66%. If now, it is desired to produce a slag in which the 
combined weight of the bases (CaO+MgO) equals the silica and alumina 
(Si02+Al 2 0 3 ) the available ' base=(51.45+1.66)—(3.43+.86)=48.82% 
In a similar manner the basic stone will show 52.66% available base, if it be 
calculated on the same slag basis. 


Limestone, which term alst> includes dolomite belongs to the sedi¬ 
mentary class of rock-formation and is widely distributed. Immense 
deposits underlie most of the area drained by the Ohio and Mississippi 
rivers. The best of these deposits are of more ancient origin than our 
coal beds, belonging to the Mississippi, or early carboniferous, period and 
previous geological periods. Some limestone is formed by chemical pre¬ 
cipitation, but the greatest portion of these natural deposits in all prob¬ 
ability originated by the accumulation of the remains of minute sea animals. 
During succeeding periods these deposits were covered to a great depth. 
They were later made accessible by processes of uplifting and erosion which 
have exposed the strata in places. 

Supply of Limestone: The main supply of limestone for Carnegie 
Steel Company comes from the Altoona, New Castle, Martinsburg and Butler 
County districts. In the Altoona and Martinsburg districts the beds have 
been folded and broken in the uplifting and lie at various angles, while in 
the other fields their position is horizontal or nearly so. In all the districts 
ment ioned the ledges representing the various deposits vary in their silica con¬ 
tent, but byaprocess of combiningthestonefrom the different ledges, the silica 
content of the different car loads is kept very constant, rarely exceeding 
5%. Great care is exercised to keep the stone as free from clay as 
possible, as this is one of the disturbing elements in uniform blast furnace 
operation. At most of the quarries, suitable crushing and screening 
devices have been installed to size the stone and remove the more 
silicious fines. 

Action of Limestone in Furnaces: In the blast furnace, limestone is 
not affected, excepting for the liberation of carbonic acid, until the lower 
levels and higher temperatures in the furnace are reached. In the smelting 
zone, or the regions just below, it combines with the gangue, forming slag, 
and also unites with varying amounts of sulphur depending upon the con¬ 
ditions of temperature and basicity of the slag. Ordinarily, about one-half 
ton of limestone is required in the production of one ton of pig iron. In 
the manufacture of steel, it plays the part of a purifying agent. Phosphorus, 
in particular, cannot be removed, commercially at least, without it. Stone 
with the lowest silica content is usually reserved for open hearth furnaces, 
that with the lowest phosphorus for furnaces making Bessemer pig iron, 
while stones with higher phosphorus content are used in furnaces making 




120 


SLAGS 


iron for basic open hearths. An analysis typical of each of these grades is 
shown in the following table: 

Table 20. Representative Analyses of the Three Different Grades 


of Limestone. 


Silica. 

Open Hearth Bessemer Pig 
.80 % 3.43 % 

Basic Pig 
1.20 % 

Iron. 

.10 % 

.30 % 

.60 % 

Phosphorus.... 

.005% 

.006% 

.033% 

Moisture. 

.10 % 

.60 % 

.60 % 

Alumina. 

.16 % 

.86 % 

•70 % 

Lime. 

54.90 % 

51.45 % 

53.88 % 

Magnesia. 

.47 % 

1.66 % 

.68 % 


Neutral Fluxes: For the purpose of making slags more fusible without 
changing their acidity or basicity, neutral substances having very low 
fusion points may be used. This practice is common in basic open hearths. 
Fluorspar is the substance generally used, though calcium chloride can be 
substituted. 


SECTION II. 

SLAGS. 

Slag is the name applied to the fused product formed by the action 
of the flux upon the gangue of an ore and fuel, or upon the oxidized impurities 
in a metal. As previously indicated, it results from the neutralization of 
bases and acids, hence corresponds to the salts of wet chemistry. The 
word cinder is used interchangeable with slag, but cinder is also applied 
to refuse in a solid form. 

Functions of Slags: On account of their fusibility, chemical activity, 
dissolving power, and low density, slags furnish the means by which the 
impurities are separated from the metal and removed from the furnace. 
Incidentally, they perform other important functions. Lying upon the 
molten metal, they serve as a blanket to protect it from the injurious action 
of hot gases, and being poor conductors, they prevent over heating of the 
metal and at the same time conserve its heat by preventing radiation. 
Since they possess the power of dissolving oxides, they mark a sharp line 
between reduced and imreduced material, and on this account serve to keep 
the metal clean. 

Importance of Slags: In the metallurgy of iron, the importance of 
slags cannot be over emphasized. In the blast furnace they furnish the 
only positive means of removing sulphur, and, as their fusion temperature 
varies with their composition, they are one of the means by which hearth 
temperature is regulated. On this account, the slag controls to the greatest 
extent the quality of the iron produced. In the open hearth, particularly 
in the basic process, the slag is the only means by which the impurities 











SLAGS 


121 


in pig iron, excepting carbon, are removed. To the metallurgist a know¬ 
ledge of the properties of slags is essential. He understands their 
chemical behavior, knows their formation temperatures, fusibility and 
fluidity, and how to control these factors. 


The Chemical Composition of Slags is within the control of the 
metallurgist, and by varying it, slags of almost any set of properties desired 
may be produced. Blags are mainly composed of two or more silicates in 
which other substances are dissolved or suspended. In the blast furnace, the 
slag will consist principally of calcium silicate, with a part of which the 
magnesium charged into the furnace will be found as a double salt. The 
same may also be the case with the small quantities of iron, manganese, 
and traces of alkali found in these slags. The sulphur removed w r ill be in the 
form of CaS, which dissolves in this mixture. As to the state of alumina, 
which usually makes up 12 % or more of the slag, there is room for doubt. 
By some it is considered as a base; by others, an acid. As noted under the 
heading of fluxes, it has the properties of both an acid and abase. Hence, 
being governed by the Law of Mass Action, it acts as a stabilizer to main¬ 
tain a kind of equilibrium between acids and bases. In a highly silicious 
slag it may side with lime to form a double silicate, while in a strongly 
basic slag it takes the place of silica in neutralizing lime and magnesia. 
Since it has very weak properties in either direction, it seems reasonable 
to suppose that, in a case where lime and silica are in stable proportions, 
all or a part of the alumina may play a neutral part and dissolve in 
the slag. In ordinary blast furnace practice, however, the sum of the 
silica and alumina (Si 02 +Al 2 C> 3 ) is considered as the acid of the slag, 
while lime plus magnesia (CaO+MgO) is taken to represent the base. 

Relation of Acids to Bases in Blast Furnace Slags: By chemical 
analysis of blast furnace slags it is found that, usually, SiC> 2 +Al 203 = 
about 48% of the slag, the ratio of Si 02 to AI 2 O 3 being about 2:1. After 
deducting from the lime enough to satisfy the sulphur, the sum of the 
remaining lime together with the magnesia (CaO+MgO) will also be about 
48%. This relation of acid to base will generally vary through a range of 
about 2 %, any increase in one being followed by a corresponding decrease 
in the other. The remaining 4% to 5% is made up of CaS and small amounts 
of ferrous and manganous oxides. As previously indicated, the ratio of 
lime to magnesia may vary somewhat without noticeably affecting the 
properties of the slag. The following results of an analysis represent a 
slag production by a furnace making basic iron. 


Table 21. Showing Relation of Acids to Bases in Blast Furnace Slags. 

Acids Bases 


Si0 2 35.02% CaO 44.03% 
A1 2 0 3 14.99 “ MgO 2.72“ 


1.16% 

1.08“ 

1.35“ 


50.01 


46.75” 


FeO 

MnO 

S 





122 


SLAGS 


Ratio of Acids to Bases in Open Health Slags: Final basic open hearth 
slags contain a much higher percentage of bases than blast furnace slags 
and a much lower percentage of acids. The lime and magnesia will always 
be more than twice the silica, alumina and phosphorus. Some open hearth 
furnacemen hold that the best results are obtained when the percentage 
of lime plus magnesia in the final slag is three times that of the silica. The 
strong basic character of basic slags is necessary for the removal of phos¬ 
phorus and the small and variable amounts of sulphur possible by the 
process. If the percentage of lime is too high, the slag will be viscous 
and retard the working of the heat. The following analysis is the average 
tapping slags from thirteen basic furnaces. 

Table 22. Relation of Acids to Bases in Basic Slags. 

Acids, per cent. Bases, per cent. 


Si0 2 

20.74 

CaO 

40.90 

A 1203 

3.55 

MgO 

9.67 

p 2 o 5 

2.85 

FeO 

10.84 

s 

.04 

Fe 2 03 

5.24 

so 3 

.23 

MnO 

5.86 


27.41 


72.51 


Acid to Base in Acid Furnaces: Both in the acid open hearth and 
in the acid Bessemer processes the slags will consist, practically, of the 
oxides of iron and manganese silicates. In both cases the silica, SiC> 2 , is 
usually about 50%; that in the acid open hearth is seldom higher than 
52% or lower than 48%, while acid converter slag will sometimes contain 
as high as 65%. The remainder of about 50% will consist of FeO and 
MnO, together with small amounts of lime and magnesia and traces of 
phosphorus and sulphur. Acid open hearth slags are self regulating as to 
the amount of FeO and MnO. These oxides, in such slags, are always 
present in such quantities that their combined percentage is equal to about 
* 46% of the slag. 

Electric Steel Furnace Slags: The composition of these slags is 
affected by the kind of steel made and the method of refinement used. 
However, the final slag of an electric steel, that is, the slag formed near 
the end of the reducing period, should be very basic, very low in iron and 
manganese content and show a goodly percentage of calcium carbide. The 
following analysis may be considered as representing a good average finish¬ 
ing slag for this process: 

Silica, 17.90%; Iron, .32%; Lime, 61.51%; Magnesia, 7.47%; Manganese, 
.35%; Sulphur, 1.30%; Calcium Carbide, .51%; Alumina, 6.00%. 

Acids Formed by Silicon: A study of slags is facilitated by a study 
of the acids of silicon. There are a number of these acids which chemists 
consider as being derived from orthosilicic acid, H 4 Si 04 or (H20)2 Si0 2 , 






SLAGS 


123 


through the loss of varying amounts of water, and are called polysilicic 
acids. When orthosilicic acid, (H 20 ) 2 -Si 02 , is set free from its salts, it 
always forms II 2 0-Si0 2 , which is called, therefore, metasilicic acid or 
normal silicic acid. The relations of these various acids are shown in the 
following table: 


Table 23. Acids Formed by Silicon. 


Orthosilicic Acid Metasilicic Acid 

(H 2 0) 2 -Si0 2 .H 2 0 . Si0 2 

2(H 2 0) 2 Si0 2 . 

3(H 2 0) 2 Si0 2 . 


Polysilicic Acids 


/ (H 2 0) 8 . (Si0 2 )2 
1 H 2 0 .(Si0 2 )2 
I (H 2 0) 4 - (Si0 2 ) 3 
\ (H 2 o) 2 . (Si0 2 )3 
1 H 2 0 .(Si0 2 )3 


Water 

+ h 2 o 
+ h 2 o 
+ 3H 2 0 
+ 2H 2 0 
+ 4H 2 0 
+ 5H 2 0 


Besides these acids, salts of other acids, which do not fit into this table, 
are known to exist, such as (H20)4-SiC> 2 . By substituting bases like CaO, 
MgO, FeO, MnO, for H 2 O in these formulas, silicates such as are formed 
in slags would be represented. In the case of sesquioxides, as Fe 203 and 
AI 2 O 3 , in which the valence of the metal is increased to three, this sub¬ 
stitution cannot be made on a basis of 1 for 1, but 2 for 3, and the formulas 
are, therefore, more complicated. 


So-called Acid and Basic Slags: In substituting a base, such as CaO, 
in the formulas above, it will be observed that the relation of base to silica 
varies in the different compounds through the wide range from 4 CaO 
combined with 1 SiC> 2 , (CaO) 4 -SiC> 2 , to 1 CaO combined with 3 Si 02 , 
CaO- (Si 02 ) 3 - The salts of the meta-and the ortho-acids, (H20)-Si02 and 
(H20)2-Si02, in which, for example, CaO is combined with 1 Si02, and 
2 CaO with 1 SiC> 2 , appear to occupy positions of equilibrium or neutrality. 
Any increase of lime increases the affinity of the slag for acids, whilst a 
decrease in lime content causes the slag to exhibit acid properties. Slags 
of this composition are also very fusible and flow readily. 


Classification of Slags: Some metallurgists classify and name the 
slags derived from the acids of silicon according to the ratio of oxygen in 
the base to oxygen in the acid, as shown in table 24: 

As illustrating the importance and value of this table, it is suffi¬ 
cient to say that it is often made the basis of calculation for the theo¬ 
retical burdening of the blast furnace. These calculations are necessary 
in dealing with new and unfamiliar materials in order to determine the 
proper proportion of fuel, ore and flux in the charge. From the type of 
slag best suited to produce the kind of iron desired, the oxygen ratio is 
fixed upon, which in turn determines the relation of acids to bases. Then, 
with the analysis of the raw materials in hand, the impurities in each are 








124 


SLAGS 


combined according to this relation. As a result of this combination the 
excess acids of fuel and ore are found, and the available base of the flux. 
These quantities, being combined in accordance with the slag ratio, will 
then, with the exception of variations in fuel consumption, fix the relations 
of the three materials. 


Table 24. Method of Classifying Slags. 


Monoxide 

Base 


Sesquioxide Oxygen 
Base in Base 


(CaO) 4 -Si0 2 (Al 2 03 ) 4 .(Si 0 2 )3 2 

(Ca0) 2 .Si0 2 (Al 2 0 3 ) 2 .(Si0 2 ) 3 1 

(Ca0) 4 -(Si0 2 ) 3 (Al 2 0 3 ) 4 .(Si0 2 ) 9 2 
CaO*Si0 2 (A1 2 0 3 ) -(Si0 2 ) 3 1 
(Ca0) 2 .(Si0 2 ) 3 (Al 2 0 3 ) 2 .(Si0 2 ) 9 1 


Oxygen 

in Acid Name Fusibility 

1 Subsilicate Fusible 

1 Monosilicate Very Fusible 
3 Sesquisilicate Very Fusible 

2 Bisilicate Moderately 

3 Trisilicate Less Fusible 


Uses of Slags: While to the metallurgist slags represent refuse no 
longer useful to his art, they may be applied to many purposes. Railroad 
ballast, road building, roof covering, concrete work, Portland cement, 
insulating materials, fertilizers, brick, and sand for mortar are some of 
the avenues open for the economic disposal of slags. 




PIG IRON 


125 


CHAPTER VI. 

the; manufacture of pig iron. 

SECTION I. 

SOME INTERESTING HISTORICAL FACTS. 

Early History of Iron: 1 While the sole purpose of this chapter is to 
describe the manufacture of pig iron as carried on at the present time, one 
or two of the many interesting topics presented by the historical aspects 
of the subject will be foimd pertinent. A word as to the origin of the use 
of iron will serve to emphasize the process of evolution through which this 
wonderful industry has passed in attaining its present state of advanced 
development. When iron was first used, no one knows, for that date belongs 
to prehistoric times. Archaeological research can only establish that it 
has been in use by man through a period of about four thousand years. 
Evidence as to the extent of its use during the first three thousand years 
of this period is lacking, but it is very probable that the metal was used 
much more extensively than the few specimens uncovered would indicate. 
The corrosive properties of iron make it, to the archaeologist, a perishable 
substance that leaves no trail. If the use of iron on this continent were 
to cease suddenly today, no evidence of its present extensive application 
would be expected a thousand years hence. Therefore, only occasionally 
is some implement or ornament found among ancient ruins. There is 
doubtful evidence of its use by the Egyptians in building the pyramids, 
about 4000 B. C. As to its use by the ancient Hebrews, by the Assyrians 
about 1400 B. C., and, more recently, by the Greeks, there can be no doubt. 
The Greeks were followed by the Romans who became somewhat proficient 
in its metallurgy. These people, through their numerous and extensive 
conquests, the success of which they no doubt owed to the use of metals 
in making their instruments of war, spread the art of extracting and 
fashioning it throughout Europe. Some knowledge of the metal, however, 
preceded them, for Caesar, crossing the English Channel, found it in use 
among the native Britons. During the Roman occupation, the industry 
grew to one of importance in England. At that time it was obtained by 
heating a mixture of ore and charcoal, probably in a flat bottom furnace 
or forge, until there had collected a small body of pasty metal which was then 
drawn and worked by hammering to make wrought iron. Such, briefly, was 
the process until 1350, when the iron makers of Central Europe succeeded in 
producing iron that would melt in the furnace and permit of casting. This 
result they accomplished in a new type of furnace, built of masonry, which 
enclosed a shaft or vertical opening in the form of two truncated cones placed 

iSee Metallurgy of Iron by Thomas Turner, published by Charles Griffin and Co. 
Ltd., London. 






126 


PIG IRON 


end to end,—in a crude way, the lines of the modern blast furnace. The lower 
frustum came to be known as the boshes, the bottom, as the hearth. In this 
furnace, ore, flux and charcoal were charged in at the top of the furnace, while 
air, under very low pressure, was blown in at the bottom. This method, was 
introduced into England about the year 1500 where, in 1619, coke was first used, 
to be followed, 200 years or more later, by the introduction of hot blast. 
In America the first iron works was established in Virginia on the James 
River in 1619, and about 100 years later (1710-1715) the first furnace using 
blast was built. Thence the industry spread, for the most part, westward. 

Old American Furnaces: The furnaces of a period as recent as one 
hundred years ago were what would now be called very crude affairs. 
Portions of some of them are still standing, and one is within a two hour 
ride erf Pittsburgh. They w r ere usually in the form of a truncated pyramid, 
twenty to thirty feet high, and constructed of stone work which enclosed 
a circular shaft, some four feet in diameter at the top and about eight feet 
at the bosh. The hearth was either round or square in cross section. 
The capacity ranged from one to six tons a day. By the year 1880, this output 
had been gradually increased to nearly 100 tons per day, with a daily 
coke consumption of nearly 300 tons. With all the basic principles in use 
for so long a time, it is remarkable that so little progress was made. 
About 1880, for reasons, which would be too lengthy to explain here, very 
rapid advancement was made, so that now there are furnaces whose daily 
output of pig iron exceeds 600 tons with a fuel consumption of less than 
2000 pounds of coke per ton of iron produced. Attention has been called 
to these facts here, because it is well to remember in beginning the study 
of the modern blast furnace, that the present method for the extraction 
of iron from its ores represents a pyrochemical process just attaining its 
highest state of development. 

The Importance of Iron: This topic needs no comment here. Pig 
iron, besides being used directly in the form of castings, is the intermediate 
from which all ferrous products are derived. Its importance is emphasized 
by the reports of the yearly productions. 

SECTION II. 

COMPOSITION AND CONSTITUTION OF PIG IRON. 

Constitution of Pig Iron: In the solid form, pig iron represents a 
very complex mixture made up of uncombined elements, chemical compounds 
and alloys. The amounts and relations of these constituents may vary 
with conditions, so that the complexity of the mixture does not depend 
wholly upon the number of elements present nor upon their amounts. Initial 
temperature and rate of cooling are two of the most important factors 
affecting the properties of pig iron. These matters are of great importance 
when the iron is to be used for castings, and to understand them fully requires 
a very extended study of the subject. This chapter has to do mainly with 
pig iron as an intermediate product in the making of steel, so it will be 
most profitable to discuss only the subject of its composition very briefly. 



ELEMENTS IN 


127 


Chemical Elements in Pig Iron: In addition to iron, the elements 
commonly occurring in pig iron are carbon, silicon, manganese, sulphur 
and phosphorus. Of these elements iron will constitute 91 to 94%, carbon 
3.0 to 4.0%, silicon .50 to 3.00%, sulphur less than .065%, and phosphorus 
.040% to 2.00% of the Whole. 

Carbon occurs in pig iron in two forms, called graphitic carbon and 
combined carbon. Graphitic carbon is practically pure carbon, existing 
in the iron in the form of tiny flakes which are distributed throughout the 
mass. It forms in the pig iron during the process of cooling, because the 
absorbing power of iron for carbon decreases as its temperature falls. 
Carbon in this form gives to pig iron the grayish black appearance so often 
seen. But in cooling, some of the carbon continues in combination with 
the iron as a definite compound, FesC, 93.33% Fe and 6.67% C. Both 
forms of carbon produce marked effects upon the properties of the iron. The 
tendency of the graphitic is to weaken, while the combined carbon, up to 
the limit of about .90%, strengthens it. In Metallography the compound 
FesC is called Cementite, and to the uncombined iron is given the term 
Ferrite. In cooling these two substances conduct themselves in a peculiar 
way toward each other. In passing a certain temperature (about 700° C.) 
they arrange themselves in layers in the definite amounts of approximately 
seven parts ferrite to one part cementite. The resultant stratified segregate 
will, therefore, contain approximately .85% C. Under the microscope these 
stratifications present the appearance of mother of pearl, whence it is 
named Pearlite. Pearlite is the strongest constituent of cast iron. When 
heated, iron absorbs carbon, and from the fusion point this absorption 
becomes very rapid. The limit, called the saturation point, beyond which 
it will not absorb any more, varies with the temperature, and is also affected 
by the amount of silicon present, a rise in the percentage of silicon causing 
a corresponding decline in the carbon content. Silicon tends, also, to 
decrease the combined carbon, and increase the graphitic. Manganese and 
Chromium have the opposite effect. Rapid cooling tends to prevent the 
formation of pearlite and graphite. In general, the more rapid the cooling 
the less the graphitic carbon and the greater the combined carbon content 
will be. 

Silicon: In small quantities silicon has little direct effect on pig iron, 
but an increase above 4% makes the iron very brittle, hence foundry iron 
will seldom contain more than 3%. In iron for basic open hearth use the 
percentage of silicon should not be higher than 1.25, as a high silicon content 
tends to flux away the lining of basic furnaces very rapidly. For the acid 
Bessemer process iron containing about 1.25% silicon is desirable, but the 
content may vary from 1.00% to 1.50%. The oxidation of the silicon 
in the Bessemer process produces a large quantity of heat, so that iron 
containing a high percentage of this element is usually referred to as hot 
iron. The amount reduced in the blast furnace is variable and depends on 
conditions of slag and temperature. Its effect on the carbon has just been 



128 


PIG IRON 


noted. Since it tends to throw the carbon out of solution, silicon is 
used to regulate the depth of chill in chilled castings. A content of one 
per cent, silicon in ordinary low sulphur iron renders it difficult to obtain 
a chill. Below this percentage the chilling properties of the iron are, roughly 
stated, in inverse ratio to the amount of silicon present. 1 Silicon also 
prevents blow holes, and tends to decrease the shrinkage in white irons. 

Manganese alloys with iron in all proportions. An alloy containing 
10 to 25% manganese is called spiegel. Alloys containing 40 to 80% man¬ 
ganese are called ferro-manganese. Up to one percent manganese tends to 
strengthen pig iron. It decreases the bad effects of sulphur, with which it 
combines, replacing iron. Its presence opposes that of sulphur, so that, with 
uniform raw materials, furnace conditions that give a high percentage of 
manganese tend to decrease the percentage of sulphur. Hence, in reason¬ 
able amounts of about one per cent, it is desirable, especially for basic open 
hearth use, where it also aids in the elimination of sulphur. In Bessemer 
practice iron with a manganese content of about .50% is desirable. The ele¬ 
ment is oxidized, and unites with silica to form a slag that fuses at a com¬ 
paratively low temperature and is very fluid, so that iron containing a high¬ 
er percentage than that indicated by the latter figure gives rise to a condi¬ 
tion in blowing known as a ‘‘sloppy” heat. As to whether manganese has 
a good or a bad effect on cast iron, there is much difference of opinion, 
some considering it almost as a cure for all troubles and others 
condemning it as a source of much trouble, especially in chilled castings. 
While it tends to hold carbon in solution, chill produced by increasing the 
manganese content alone is soft and tends to spall 1 . In moderate amounts 
it is said to prevent cracking of the surface and also spalling to some 
extent, especially in chilled rolls. Nearly 75% of the total amount of 
manganese charged into a blast furnace is obtained with the metal. 

Sulphur in pig iron is generally supposed to be injurious, though 
recently the statement that the inferior qualities exhibited by high sulphur 
iron are due entirely to its presence has been questioned. Nevertheless, as 
sulphur in steel is considered undesirable and as the blastfurnace affords the 
only positive means of reducing it, pig iron containing less than .05% is 
desirable for making steel by all the fusion processes Sulphur with iron 
forms iron sulphide, which is soluble in the metal and has a melting point 
that is lower than the other constituents of the iron. According to some 
authorities 1 , this sulphide in iron used for castings has a three fold influence. 
First, it tends to hold the carbon in combined condition, hence can be 
used to increase the depth of chill in chilled castings; second, its low 
melting point causes it to segregate as the iron solidifies, thereby causing 
the condition in castings known as bleeding; third, it increases the shrinkage 
of the iron to a marked degree, thus increasing the difficulty of making 
accurate castings and increasing the tendency to cracks which are a result 

iSee The Principles, Operation and Products of the Blast Furnace, by J. E. 

Johnson, Jr. Published by McGraw-Hill Book Company Inc., New York. 





GRADES OF 


129 


of the high shrinkage. The chill imparted by sulphur is a very hard one, 
but is very brittle and somewhat unreliable. 

Phosphorus is the only element entering the blast furnace over which 
the skill of the furnaceman has absolutely no control. Its compounds are 
completely reduced, so that all the phosphorus in the raw materials is found 
in the metal. Therefore, its content must be regulated by proper selection 
of raw materials. High phosphorus causes a slight brittleness in pig iron, 
and has a marked effect upon the total carbon. Ferro-phosphorus containing 
about 15% phosphorus is carbonless. Lesser amounts permit a pro¬ 
portionate increase of carbon, so that the total carbon in an iron containing 
.2% phosphorus may be as high as 4%. In this respect its action is not 
selective, since the ratio of combined to graphitic carbon is not affected. 
Phosphorus is known to form a compound, Fe 3 P, with iron, but it is able 
apparently to combine with it in several proportions. Ferro-phosphorus 
containing as much as 25% phosphorus is now manufactured. In iron for 
casting, phosphorus exercises a beneficient effect. It tends to eliminate 
blow holes, decreases shrinkage, and increases the fluidity. Above .5% 
it begins to weaken iron, so the amount used will be governed by the use 
to which the casting is to be applied. 

Grading Pig Iron: Pig Iron is graded by chemical analysis. There 
are several systems employed, many of which are somewhat elaborate. 
The following table, which includes other important blast furnace products 
as well as ordinary pig iron, shows one of the simplest methods of classi¬ 
fication: 


Table 25. The Metallic Products of the Blast Furnace. 


RANGE IN PERCENT. OF 


GRADE 

Silicon 

Sulphur 

Phosphorus 

Manganese 

Total Carbon 

No. 1 Foundry. 

2.5 to 3.0 

Under .036 

.25 to 1.00 

Under 1.00 

3.50—4.25 

No. 2 Foundry. 

2.0 to 2.5 


.045 

.25 to 1.00 

“ 1.00 

3.50—4.25 

No. 3 Foundry. 

1.5 to 2.0 


.060 

.25 to 1.00 

“ 1.00 

3.50—4.25 

Malleable Casting... 

.75 to 1.5 


.050 

.2 

“ 1.00 

3.50—4.25 

Forge. 

About 1.50 


1.00 

1.0 

1.00 

3.50—4.25 

Acid Bessemer. 

1.00 to 1.50 


.050 

0.1 or less 

About .50 

3.50—4.25 

Basic Bessemer. 

Under 1.00 


.050 

2.00 to 3.0 

Under .50 

3.50—4.25 

Bow Phos. Acid Iron 

“ 2.00 


.030 

.030 

“ 1.00 

3.50—4.25 

Basic. 

“ 1.25 


.050 

.100 to 1.00 

1.00 to 2.50 

3.50—4.25 

Spiegel. 

About 1.00 


.050 

.150 

18.0—22.0 

5.0 —6.0 

Ferro-Manganese,. . . 

.50 to 1.00 


.030 

.10 to .30 

78.0-82.0 

5.0 —7.0 

TT’prrn-ft il ip.nn 

8.0 to 15.00 


.070 

.10 to .50 


1.00—2.00 

Silico-Spiegel. 

8.0 to 15.00 


.010 

.15 

15.00-20.00 

• 

































130 


BLAST FURNACE 


SECTION III. 

A BRIEF OUTLINE OF THE PROCESS AND EQUIPMENT FOR 
THE MANUFACTURE OF PIG IRON. 

Trend of Modern Iinprovements: With the preceding brief summary 
of the history, importance, and composition of pig iron in mind, the process 
by which it is manufactured furnishes a theme of great interest. Apropos 
of this idea, however, it is to be observed that a description of the modern 
methods of manufacture is rendered difficult both by the complexity of the 
details of the process and by its recent rapid development. As already 
pointed out, the fundamental principles have remained unchanged since 
the foimding of the process, because experience has demonstrated that this 
process is the most practical. All improvements, then, have been made 
with the aim of increasing the production and at the same time decreasing 
the cost. These objects have been attained to a degree almost approaching 
perfection by the use of materials of greatest purity, selected through 
chemical control, by increasing the size of furnaces, by economies in fuel 
consumption, and by improved methods of handling the materials. The 
result is that the small plants of 100 years ago have been succeeded by 
complex and gigantic affairs. As the greatest changes have been brought 
about since 1880, a comparatively recent date, the blast furnace plant is 
just approaching the uniformity of perfection. Furthermore, since the 
improvements have been contributed by a great number of men, it is not 
to be wondered at that an inspection of the industry will reveal not only 
different stages of development but also many different methods of attaining 
the same end. The aims and fundamental principles being the same, 
however, the numerous plants, w T hile differing greatly in detail, will present 
certain similarities in their gross features which may profitably be reviewed 
before proceeding with the detailed description. 

Essentials of the Process: Essentially, the present process for the 
extraction of iron from its ores consists in charging a mixture of ore, fuel, 
and flux in proper proportions through a specially constructed opening in 
the top of a tall cylindrically shaped furnace called a blast furnace, while 
heated air is simultaneously blown in near the bottom through openings, 
called tuyeres, the nitrogen of the air together with the products of com¬ 
bustion and reduction passing upward and escaping through openings at 
the top. These parts of the process, being almost continuous ones, are 
accompanied by the periodic removal of a part of the impurities in the 
form of slag at an opening between the tuyeres and the bottom, and by a 
like removal of metal through a larger opening at the bottom. In order 
to carry out these operations on the large scale previously mentioned, it 
is evident that extensive equipment is required. 

Essential Equipment: The central feature in this equipment is the 
furnace, which is provided with apparatus for hoisting the materials to the 
top and with ladles for containing slag and molten metal, to which is some- 




EQUIPMENT 


131 


times added casting beds or pig machines for casting the metal into “pigs” 
of convenient size, and slag granulating pits. Next in importance follows 
the blowing engines for producing the blast, then the stoves for heating 
it. Of great importance is the pumping station, the function of which is 
to furnish the great quantities of water needed for steam, for cooling, etc. 
As the gases that escape from the top of the furnace are combustible, 
apparatus for their most efficient disposal is desirable. They are used to 
heat the stoves and to generate power either by burning them under boilers 
or in gas engines, in which case they must be cleaned of the large quantities 
of flue dust which they carry out of the furnace. As the moisture in the 
air affects the efficiency of the furnace, some modern plants will be provided 
with apparatus for drying the blast. Referring again to the solid materials 
of the charge, modern equipment requires a stock house, topped by bins, 
in which the ore, fuel and flux may be temporarily stored and conveniently 
removed for weighing or measuring before delivering it to the hoisting 
device. Adjacent to the bins will be located the stock yard containing the 
ore pile, which is spanned by the ore bridges. A car dumper, advantage¬ 
ously situated, will complete this part of the equipment. Finally, the various 
parts of the plant will be made accessible by a system of railways for trans¬ 
porting the materials. 


SECTION IV. 

CONSTRUCTION OF THE BLAST FURNACE PROPER. 

The Gross Features of the Furnace Proper: The modern blast 
furnace is a tall circular structure, 90 to 100 feet high, built of fire brick, 
reinforced externally by a close fitting steel shell and encasing internally 
a circular space of varying diameters. This space is divided into three 
main parts. The bottom section, called the hearth or crucible, is cylin¬ 
drical in form and some 10 to 12 feet deep in the larger furnaces. The 
second section, having an altitude of some 12 or 13 feet, is called the bosh. 
It is in the form of a frustum of a cone, which, in an inverted position, tops 
the crucible with its smaller base. Setting above the bosh in an upright 
position with an altitude of about 70 feet, is the stack. Formerly its outline 
was also that of a frustum of a cone, but recent studies of furnace lines 
indicate that the slanting lines of the cone should be changed to the vertical 
for a distance of 4 or 5 feet above the bosh, and for about 10 feet from 
the lower bell at the top. The whole is now capped by the furnace top, 
which completes the list of the gross features of the furnace proper. 

The Foundation: Before proceeding with the details of the parts 
noted above, the foundation should be considered. In view of the immense 
weight which it is required to support, this part of the furnace is of great 
importance, because any extensive settling of the furnace aftei it is in 
operation would result in serious troubles and probably put it out of com¬ 
mission. The depth of the foundation will vary with the conditions of the 



132 


BLAST FURNACE 


rock materials on which it is to stand. If these be sand or clay, it may 
be necessary to drive piling for a depth of many feet, and upon this begin 
the foundation. On the other hand, if solid and firm rock underlies the 
location for the furnace, an excavation to this rock is all that is required. 
A proper bed having been found or otherwise provided, the foundation is 
started and built up several feet with concrete, which extends some distance 
outward beyond the floor of the furnace. The remainder of the foundation 
is then made up of common brick of good quality and strength, except the' 
space directly beneath the hearth and walls of the furnace, where firebricks 
are used. 

• 

The Hearth or Crucible is the portion of the furnace which serves 
as a receptacle for the molten metal and slag. It is constructed of fire 
brick of the best quality; its wall is usually sixty inches or more in thick¬ 
ness; and it may be protected in places with water cooled plates, if the fur¬ 
nace is of recent construction. At the bottom the walls of the hearth are 
usually stepped out into the interior of the hearth for four or five courses 
of brick. This construction gives the bottom surface a slight basin shape, 
and tends to hold the bottom brick inplace. The hearth varies in diameter 
and depth with the size and capacity of the furnace. In the larger ones, it is 
about eighteen feet in diameter and eleven feet deep. Externally, it is 
reinforced by a heavy metal jacket made of steel plates that are riveted 
together, or of iron castings in segments that are jointed and bolted together. 
Jackets are always cooled, those of cast iron by internal circulating 
systems, and those of steel by external sprays. The upper diameter of this 
jacket is smaller than the diameter at the base, so that the jacket will 
better hold the walls of the hearth in place by offering resistance in oppo¬ 
sition to the buoyant forces of the bath and slag. 

The Bottom of the crucible is built of fire brick, sometimes in the 
form of large blocks, which are laid on end with closely fitting joints in 
order to prevent intrusion of metal. Bottoms vary in thickness from about 
six feet in the smaller furnaces to about twelve feet in the large ones. The 
bricks are almost entirely replaced in time by metal, which, collecting in 
a solid mass, often weighing many tons, is known as the salamander. 

Tapping Hole: Situated at some convenient point in the circumference 
of the hearth and just above the top course of stepped-in brick is the tapping 
hole or iron notch. If the bricks are not stepped-in, the opening will be 
at the bottom. It may be a square opening in the brick about 8x8 inches t or 
an oblong or rectangular one 6x8 inches on the inside. The outside dimen¬ 
sions may be somewhat larger to permit of easily inserting the tapping 
tools. Proper provision is made for the protection of the hearth jacket 
at this point. During the tapping of iron, the metal structures directly 
above the tapping hole are protected with a splasher. 



CONSTRUCTION 


133 



Fig. 20. Vertical Section of a Modern Blast Furnace. 


« 




















































































134 


BLAST FURNACE 


Cinder Notches: There is usually but one cinder notch. This 
opening may be placed at any convenient point in the circumference of the 
hearth at a sufficient height above the tapping hole to permit the collection 
of the desired amount of iron between tappings. In the larger furnaces it 
is about six feet from the floor of the hearth and four to five feet above the 
tapping hole, being generally placed 45° or 90° from this opening. Unlike 
the tapping hole, this opening is water cooled to protect the brick from the 
fluxing action of the slag. Hence, the opening in the brick work is larger, 
being about one foot in diameter inside and increasing to about two feet on the 
outside. In this circular cone-shaped hole in the brick the cooling devices 
are placed. These are castings, usually made of copper, and consist of acin= 
der cooler, an intermediate, or monkey, cooler, and a monkey.The cinder 
cooler is in the form of a hollow frustum of a cone. It is about two inches 
thick, and, between its walls, proper provision is made for the circulation 
of water. It is made to fit the hole in the brick work and is tamped securely 
in place with fire clay. The opening in this cooler is then reduced by 
inserting into its inner end the close-fitting intermediate cooler, which is 
constructed like the cinder cooler, but smaller and shorter. Finally, the 
still smaller monkey, through which water circulates also, is inserted, 
reducing the opening to about two inches. A short iron rod, called a bott, 
tapered to fit the monkey and attached to a long steel rod which serves 
as a handle, is used to close the opening. The sizes of the three coolers 
are regulated so that the large diameters of the monkey and intermediate 
cooler fit the smaller diameters of the intermediate and cinder coolers, 
respectively. Thus, the monkey, when in position, is wholly within the 
furnace. In each of these castings and within their topmost quadrant, 
when in position for service, are provided two threaded holes into which 
the pipes for ingress and egress of the cooling water may be inserted. 

Tuyeres: The tuyeres, from ten to sixteen in number, are distributed 
symmetrically about the upper circumference of the hearth just below the 
boshes. Their function is to provide passages for the blast. They also 
determine the height to which the slag in the furnace may rise. In the 
large furnaces, this height is about three feet. Fitted into the opening in the 
brick, flush with the wall, both internally and externally, is the tuyere 
cooler. It is similar to the cinder cooler, and set tight with fire clay. The 
tuyere itself, of copper, presents an internal diameter of from four to seven 
inches, while its external diameter is such as to permit it to fit snugly into the 
smaller end, or nose, of the cooler and project several inches into the furnace. 
Like the cooler, the tuyere is water cooled and is tapped at two places in 
the top quadrant for the insertion of water pipes through which a copious 
stream of water must be kept flowing to avoid burning it. 

Tuyere Connections : With one end fitting closely against the tuyere, 
is a horizontal cast iron pipe, about five feet long, called the blow pipe, 
sometimes the “belly” pipe. Through it the hot blast is delivered to the 




CONSTRUCTION 


135 


tuyere from the tuyere stock, to. which the names leg pipe, boot leg and 
pen stock are also often applied. The blow pipe may be slightly larger in 
diameter at one end than at the other, and both ends are turned to fit into 
slight sockets in the tuyere and the tuyere stock. It is held in place with 
the smaller end fitting into the tuyere by pressure from the tuyere stock, 
which is provided with a spiral spring and connecting rod, attached to the 
hearth jacket, for this purpose. The tuyere stock curves upward immedi¬ 
ately on leaving the blow pipe, and a hole in a lug on its under part gives 
an opening through which the connecting rod passes through the coiled 
spring to the hearth jacket where it is anchored. The heavy spiral spring, 
which provides pressure and at the same time allows motion due to expan¬ 
sion and contraction of the tuyere stock and blow pipe with changes in 
blast temperatures, is placed between this lug and a large brass nut on the 
other end of the connecting rod. The nut is made of brass so it will not 
rust and be difficult to operate. In the outer part of the curve in the tuyere 
stock, and in the center line of the blow pipe and tuyere is a small opening, 
closed by the tuyere cap or “wicket,” through which a small rod may 
be inserted to clean out the tuyere without removing the blow pipe. 
The wicket must be of such a form that it may be opened readily at 
any time and still be practically gas tight. To meet these conditions 
the wicket is constructed on the principle of the ball and socket joint. 
The ball is attached to the end of the short arm of a right angle lever and 
is held tightly in the socket by a ball weight attached to the long arm. 
A smaller opening, called the peep hole, in the tuyere cap is covered with 
glass, which permits inspection of that portion of the interior of the furnace 
directly in front of the tuyeres. Extending upward, the tuyere stock 
connects with the nozzle of the goose neck, to which it is clamped by means 
of lugs and keys that fit into seats of hanging bars. The goose neck then 
turns at right angles and extends horizontally to the neck of the bustle 
pipe to which it is fitted and securely fastened by flanges and bolts; or the 
tuyere stock may lead at an angle to the horizontal directly to the lower 
part of the bustle pipe. The bustle pipe is the large pipe, about four 
feet in outside diameter, which encircles the furnace and distributes the 
hot blast to the tuyeres. All these pipes, down to the blow pipe, are 
lined with fire brick. The bustle pipe is fed by the hot blast main which 
terminates at the stoves. It is of about the same size as the bustle pipe, 
and lined with nine to twelve inches of fire brick. 


Boshes: As previously described the bosh is that part of the furnace,, 
just over the hearth, where the greatest diameter is attained. No shell! 
cr jacket covers the exterior of the bosh. A standard bosh is constructed 
in the following manner: Starting at the top of the hearth, the brick 
work, 30 inches in thickness, is stepped outward, externally, nearly six 
inches for each twelve inches of vertical rise. Each step-out is supported 
by means of a heavy steel band, or a pair of bands, called bosh bands*. 




136 


BLAST FURNACE 


Inserted in the walls of the boshes, through cast iron ‘‘boxes ,’' placed in 
the brick spaces between pairs of bosh bands, will be found cooling plates, 
called the bosh plates, in horizontal rows about two feet apart, measuring 
vertically. The plates in each row will be about four or five inches apart, 
and the plates in the different rows will be staggered vertically, breaking 
joints like brick work. This construction adds to the cooling efficiency of 
the plates. There are several different makes of bosh plates, but the more 
common ones will be somewhat wedge-shaped, with a flat bottom and oval 
top, and about four inches thick at the point of their greatest altitude. They 
are hollow and have inserted in them, usually at opposite corners, two 
pipes through which water flows continuously. These plates are necessary 
to help protect the brick work, for, being just above the tuyeres in the 
zone of fusion, the bricks here receive the highest heat of the furnace. 
Formerly the plates extended almost through the wall in new work, 
usually to within one course of brick, but it was found that this course of 
brick is soon cut away after the furnace is blown in, so now the plates 
extend entirely through the wall from the first. 

Mantle: At the upper limits of the bosh is found the mantle, con¬ 
forming to the shape of the furnace at that point and totally encircling it. 
The mantle is made up of heavy steel plates and angles, upon which rests 
the weight of the stack. It is supported by a series of cast iron pillars 
or fabricated steel structures, which rest on foundations supported by the 
main furnace foundation. This construction allows the entire bosh and 
hearth to be removed without disturbing the rest of the furnace. 

Shaft, or Stack, and In=Walls: The shaft comprises all that part 
of the furnace which is located above the boshes. The wall of this shaft is 
usually, in an imaginary way, divided into three almost equal parts, called 
the upper, middle and lower inwalls. Up to this point, the construction 
for all furnaces is fairly uniform as to general features. But as to the 
inwalls three types are employed, namely, the thick, the intermediate, 
and the thin wall. The construction necessarily differs for these different 
types. Therefore, each type is best described separately. 

Thick Wall Type: The inwalls of this type are about five feet thick, 
and are inclosed in a heavy riveted steel shell about one-half inch thick. 
The shell is usually made oversize to provide a small space between it and 
the brick work, in which space is tamped lightly a packing of loam and 
granulated slag, to allow for the expansion and contraction of the inwalls. 
Thick walled furnaces are seldom water cooled above the bosh, and their 
walls furnish the sole support for the top. 

The Furnace Lines and Bosh Angles of furnaces of the thick wall 
•type differ somewhat. In modern blast furnace construction the lines of 




CONSTRUCTION 


137 


the furnace, by which is meant the lines formed by the inner edges of a 
vertical section through the center, with their enclosed angles, are con¬ 
sidered of great importance. In the old furnaces, the lines of the inwalls 
were straight, and the boshes somewhat flat with corresponding sharp 
angles. But with the fine ores from the Lake Superior district, experience 
has taught that much better practice is obtained with more nearly vertical 
lines. So, in the latest type of furnace the lower inwall will rise verti¬ 
cally for several feet, the boshes will be steep, and the upper inwall will 
drop vertically for a distance of about ten feet from the stock line. Bosh 
angles, that is, the angles at the top of the bosh, which its wall forms 
with a horizontal from the center of the furnace, are now being increased 
from about 75° to 80°. These steeper boshes are proving to be an 
important improvement. 

Intermediate, or Semi=Thin, Wall Type: In the intermediate type, 
the walls are about three feet thick, and to protect the brick as much as possible, 
cooling plates, similar to bosh plates, are inserted in the lower inwall. They 
may extend for a distance of from twenty to forty feet above the bosh. 
The top in this type is sometimes supported by columns of fabricated steel, 
but in the majority of cases it is supported by the walls as in the thick 
walled type. The inwalls are surrounded by a steel jacket as in the thicker 
type, the only difference being in the necessary openings for the coolers. 

Thin Walled Type: In this type the inwalls are from nine to eighteen 
inches thick, the top is always supported by structural work, and the shell must 
be cooled throughout its entire length. This cooling may be done in three 
ways. One method consists in spraying the jacket with water, conducted 
through suitably arranged pipes and enclosed by a light “splash jacket” which 
conforms to the size and shape of the stack. In the second method the 
shell is encircled by a series of deep and narrow horizontal troughs through 
which water is kept flowing from the top to the bottom of the furnace, 
overflowing from each trough to the next succeeding lower one. Each of 
three or four of these troughs drain separately to a common point where 
the temperature of the water can be noted. In the third type, the entire 
outer surface of the stack is kept covered with water by means of a spiral 
trough which, slightly separated from it, encircles the stack from top to 
bottom. This trough is kept full of water by a series of feed lines that enter 
it at various points in the spiral. 

Furnace Linings: The brick-work which forms the hearth, bosh and 
inwalls of a furnace are referred to as its linings. All the brick used in 
the construction of these parts are made of fire clay, and are of three kinds, 
known as hearth and bosh brick, inwall brick and top brick, each of 
which is made of such materials and in such a way as to render it best adapted 
to the conditions it is to be subjected to in service. The hearth and bosh 
brick are required to resist a very high temperature and the action of flux 




138 


BLAST FURNACE 


and slag; inwall brick must be able to withstand abrasion at a moderately 
high temperature; and top brick, always at a comparatively low temper¬ 
ature, must resist the impact and abrasive forces of the charges as they 
are dropped into the furnace. These different qualities in the different 
bricks are obtained by varying the method of manufacture especially with 
respect to composition, degree of grinding and temperature of burning. 
As to the former factor, three classes of materials, or clays, are available. 
These are flint clay, plastic clay and calcined clays. Mixtures employed 
by different manufacturers are by no means uniform, but the following 
may be taken as fairly representative of good practice. 


Table 26. Showing Data Relative to Fire Brick for Use in 

Blast Furnaces. 


PROPORTION OF 


Kind of Brick 





Final 


Flint Clay 

Calcined Clay 

Plastic Clay 

Manner of 

Temperature 




• 

Grinding 

of Burning 

i 

Hearth and 






Bosh Brick 

50 to 65% 

20 to 35 % 

14 to 16% 

Coarse 

1350°C 

Inwall Brick 

40% 

30 to 40% 

20 to 30% 

Medium 

to 

Top Brick. . 

0 to 30% 

1 

30 to 50% 

40 to 50% 

Fine 

1450 °C 


All the materials, irrespective of the kind of brick, should be and are 
of the best quality obtainable, and the brick are carefully inspected before 
being put in place in the furnace. The three kinds of brick are distinctly 
marked by the manufacturer, so that the danger of wrongly placing a brick, 
a top brick in the hearth, for example, may be avoided. Great care is 
exercised with respect to brick, because the life of the furnace depends in 
a large measure upon the lining, and the item of cost for brick is not a small 
one. In the construction of one of the large modern furnaces, close to the 
equivalent of 800,000 nine inch brick are required, and the average con¬ 
sumption of brick is a little more than two brick for each and every ton of 
pig iron produced. Fire bricks are always laid in a thin slurry composed 
of fire clay and water. The slurry is applied by pouring it on the top of 
each course with a dipper, and is followed immediately by the next course of 
bricks, which are hammered into place to squeeze out all the fire clay except 
that required to compensate the inequalities of the brick. 



















CONSTRUCTION 


139 


Water Trough: Encircling the furnace bosh, inside of and above the 
bustle pipe, will be found one or more water troughs into which the water 
supplying the numerous cooling plates is discharged in visible streams, 
thus providing means of determining when a plate is burned out. The 
water, flowing from these troughs into a well, may be pumped back through 
the cooling system, and thus be used over and over. 


Tops: At the present time furnace tops are somewhat complicated 
affairs. In olden times the tops of furnaces were left open, the escaping 
gases being allowed to burn in the air. In the year 1814, these waste gases 
began to be employed in France for the purpose of burning bricks and heating 
small furnaces. The first attempt to heat the blast by utilizing these gases 
was made in 1834, and consisted in laying, across the tunnel head, pipes 
through which the air blast passed in going to the tuyeres. It was not 
till 1845 that a plan was evolved by which the gases could be used to heat 
the stoves. To effect this purpose, changes in top construction were neces¬ 
sary. At first the gases were merely drawn off by the chimney draft of 
the stoves through openings below the stock line. The arrangement, 
know^p as the bell=and=hopper, or cup=and=cone, was not put into use 
till 1850. It consisted in closing the top of the furnace by means of a large 
circular hopper, the smaller opening of which was closed by the bell 
that could be lowered and raised at will. With the bell raised against the 
hopper, the materials were dumped into the hopper; then the bell was lowered, 
and the charge dropped into the furnace. As large quantities of gas escaped 
with each lowering of the bell, this device was improved by the double= 
bell=and=hopper, which is of comparatively recent origin. Essentially, 
this improvement consisted in placing a second but smaller bell-and-hopper 
above the first, and providing a gas tight space of large size between the 
two. The raw material, upon being hoisted to the top, is first dropped or 
dumped into the upper hopper, whence it may fall into the larger hopper 
below when the small bell is lowered. The small bell being raised against 
the upper hopper, the large bell is lowered, and the charge falls into the 
furnace without the escape of gas. The bells are made of cast steel, in one 
piece, and of such a slope, 45° to 55°, as to permit the charge to slide off 
readily. They are usually supported from their top centers by means of a 
rod and a sleeve, each attached to a counterbalanced lever operated by 
means of a steam or air cylinder or an electric motor, controlled from the 
ground. The large bell is attached to the rod and the small bell to 
the sleeve. The hoppers, of cast steel or iron, will generally be made up in 
sections, which are securely bolted together. They are provided with 
a removable, but gas-tight, flange and extension ring, also in sections, 
which permit the bell to be readily removed in case a change is 
necessary. The details of this construction differ somewhat to conform 
to the introduction of improvements, with the type of hoist, and with the 
ideas of the different builders. 




140 


BLAST FURNACE 


Stock Distributor: One of the alleged improvements in the bell- 
and-hopper device is that of the stock distributor. There are several types 
of these distributors employed, a description of which would not be profit¬ 
able here. However, the object aimed at by such devices may be explained 
thus:—It is apparent that, in a mechanically filled furnace, when the raw 
materials are dropped into the receiving bell, the larger lumps of ore and 
stone will have a tendency to roll and thus collect either around the edges 
or to one side or the other. The same things will also happen upon dropping 
the charge into the furnace. This tendency results in more or less open 
and continuous channels being formed through the materials and extending 
from the top towards the bottom of the stack. These channels offer less 
resistance to the passage of the blast than the remainder of the materials, 
or the fuels, with the result that a disproportinate quantity of gas passes 
through them. This condition, called channelling, results in higher tem¬ 
peratures throughout these passages, with the consequent cutting away of 
the walls where these channels come in contact with them. It is to over¬ 
come this defect that the various devices formerly mentioned have been 
designed. 

Hoisting Appliances: The old time method of charging by fiand 
having been entirely superseded by automatic mechanical charging, there 
are now in use two types of these devices, namely, the skip hoist and the 
bucket hoist. In both cases there is an incline, a fabricated steel structure, 
extending from the top of the furnace to or below the bottom of the stock 
house; and over the tracks of this incline the materials charged into the 
furnace must pass. In the skip hoist, the conveying vessel is a small open- 
ended steel car, called a skip, that automatically dumps the materials upon 
the little bell-and-hopper. Skip hoists are generally provided with double 
tracks, so that while a loaded skip is passing up the incline an empty one 
is descending. In the bucket hoist the solid materials are raised in a 
bucket, suspended from a truck or carriage, that drops the charge into the 
space above the large bell direct. When in position for dropping the charge, 
the bucket, being itself provided with a small bell at the bottom, takes the 
place of the little bell and hopper. During the time the bucket is filling 
at the stock house, the opening left in the top is closed with a 
special gas seal. 

Top Openings: The smallest opening in the top of a furnace is the 
try=hole. In operating a furnace it is necessary to be able to determine 
the position of the stock line. This is done by means of the stock i ndicator, 
which is a rod of steel passing through and fitting the try-hole loosely so 
that one end rests upon the stock, while the other is attached to a small 
steel cable that leads to the stock house or the cast house below. Some 
stock indicators are automatic and self-recording. For the escape of the 
gases, from two to four large openings, called offtakes, are provided. They 



CONSTRUCTION 


141 


pierce the furnace top just beneath the large bell. From these openings, 
about four feet in diameter, lead fire-brick lined pipes which converge into 
one large pipe called the downcomer or downtake. Into openings, either in 
the offtake pipes or in special openings in the top, are inserted the explosion 
doors. These doors, located usually in the ends of upright pipes arranged 
so as to prevent ejection of material from the furnace, are really valves 
which are adjusted, either by weights or by a mechanical means, to open 
at a certain pressure. They are designed to relieve pressure and so prevent 
possible injury to the top by slips in the furnace. The bleeder is a tall 
vertical pipe, usually inserted on the higher surface of the offtake pipe 
leading to the downcomer, to allow surplus gas to escape. It is closed 
with a valve on the top, which opens automatically, and may also be 
opened from the ground. Bleeders are usually lined with one course of 
fire brick. 

General Consideration for Top Construction: As previously 
pointed out, there are many types of top, and the description above is 
intended to give a general idea of the essential parts and their uses only. 
The chief endeavor in top construction is to perfect the distribution of the 
stock entering the furnace stack, and either eliminate or compensate for 
as many irregularities as possible. However, in attaining this end, sim¬ 
plicity must be considered, as any great amount of mechanism on the top 
of a furnace is objectionable. It is important to prevent large material 
from being thrown out of the furnace in case of slips, and as little dust as 
possible should be carried out by the gases. Hence, in the most recent 
construction, the offtakes enter vertical up takes, closed at the top by 
explosion doors, and are taken off the furnace as high above the stock line 
as possible, preferably at four points equally spaced on the circumference. 
The downcomer connections are taken off part way up on these up-takes. 
In locating the uptakes in furnaces of most recent construction, care is 
taken to see that they do not enter the furnace directly over the tapping 
hole, cinder notch, or the entrance of the blast main to the bustle pipe, 
because, these being the most active points in the furnace, this 
arrangement will tend to give a more even distribution of the gases 
through the stock. 

Runners: Though not given much prominence in blast furnace dis¬ 
cussions, the runners, through which the slag and metal are carried away 
from the furnace, constitute an essential part of the furnace proper. These 
are metal castings in the form of deep troughs which are made in sections 
laid end to end and buried so that their top edges are flush with the floor 
of the cast house. The trough leading from the cinder notch will, of course, 
be elevated. It forms an uninterrupted passage for the slag from the cinder 
notch to the slag ladle or granulating pit. The metal runner is more com¬ 
plicated. Beginning as a very deep trough at the tapping hole, it is inter¬ 
rupted at the end of about 10 feet by the skimmer, a device for separating 



142 


BLAST FURNACE 


the metal from the slag that comes near the end of a cast. There are 
two branches here, one for carrying away the slag and another for draining 
the metal from this part of the skimmer trough after the cast. From the 
skimmer the main trough is drained by branches leading to casting beds 
on the floor of the cast house, or what is more common now, to hot metal 
ladles on a track far enough below the floor of the cast house to permit 
the metal to flow into them from above. Before casting, these troughs 
are given a heavy coating of a loam or clay wash, which acts as an insulator, 
protects the trough from the hot metal and facilitates the subsequent 
cleaning up. Without this wash the hot metal would either chill in the 
trough or melt it away. 


SECTION V. 

BLAST FURNACE ACCESSORIES. 

The Stoves, of which there are nearly always four to a furnace, are 
first in importance under the heading of accessories, being an absolute 
necessity in modern blast furnace operations. This importance is due to 
their function of heating the blast. The first stoves used were constructed 
of iron pipes enclosed in a brick structure through which the blast passed 
to the furnace, the gases from the furnace being burned as they circulated 
outside and around these pipes, the recuperative principle. Then it was 
found that the regenerative principle is much more efficient, so that now 
stoves are built entirely of brick. Essentially they are brick walled cylin¬ 
ders, enclosing a combustion chamber and a system of regenerative flues. 
Externally, the brick wall of a stove is reinforced and supported by a steel 
shell of riveted plates. The top of the stove is dome-shaped. Generally, 
the stoves are as high and almost as wide as the furnace itself. They 
vary in size with the size of the furnace. For the largest furnaces 
they are approximately 100 feet in height and 22 feet in diameter. Inter¬ 
nally, the combustion chamber will extend from the bottom to the top of the 
stove, and may be located at the center, in which case they are called 
center combustion stoves, or at the circumference, as in side combustion 
stoves. The regenerative flues are filled with brick checker work, the 
checkers being so laid as to form a system of vertical flues, from five to 
nine inches square, which extend from the rider walls on the bottom to the 
top of the stove. The arrangement of the flues also furnishes a means of 
classifying stoves. Stoves in which the gases from the combustion chamber 
pass through only one regenerative flue, are called two=pass stoves, while 
in three=pass and four=pass=stoves they pass through two and three 
regenerative flues, respectively. Two-pass and three-pass types are the 
most common. Since the combustible gases are burned at the bottom 
always of all stoves, it follows that in two-pass stoves the products of 
combustion, passing through the checkers, must leave the stove at the 



STOVES 


143 


bottom, hence the opening to the stack on two-pass stoves is at the 
bottom. At some plants, stoves of this type are provided with individual 
stacks which rise along the side of the stove, but in other plants under¬ 
ground flues from a number, usually a set of four, of such stoves empty 
into a single stack, centrally located. In the three-pass type the hot gases 
are returned to the top of the stove, there to escape through an opening 
in the dome into a stack which tops the stove. 

Stove Burners and Valves: Since the checkers in stoves are alter¬ 
nately heated by the products of combustion of a gaseous fuel in their 
passage to the open and cooled by the passage of the air or blast in an 
opposite direction and under pressure, a system of burners and gas tight 
valves are required. The burners are usually very simple in construction, 
consisting of a movable gooseneck mounted on a rack attached to the 
terminal of a vertical section of an underground gas flue in such a manner 
that the horizontal portion extends into a gas port in the side of the stove. 
A plate, or valve cover, is attached to the base of the goose-neck or the rack, 
so that racking the goose-neck back and forward automatically closes and 
opens the connection to the gas main. There are a number of moie com¬ 
plicated and patented burners in use, which aim to increase the efficiency 
of the stove 1 . The valves present such a variety of forms that a detailed 
description of all cannot be attempted. The essential ones are named 
from their location. The gas valve has already been described in con¬ 
nection with the burner. The chimney valve is located at the base of the 
stack, its office being to prevent the escape of air through that opening 
when the stove is on blast. In three-pass stoves this valve is controlled 
from the ground by means of chain, or cable, and pulleys. The cold blast 
valve is located in the air line, which branches from the cold main from 
the blowing engines at a point just ahead of its entrance into the stove. 
As it is never subject to high temperatures, an ordinary form of gate valve 
may be used. In the three-pass type of stove this valve will also be at 
the top. The hot blast valve controls the exit of the blast from the stove 
through which the air passes. The blast being highly heated at this 
point, the hot blast valve must be constructed to withstand high 
temperature. It is usually of the mush-room type, and water cooled. 

Other Stove Openings: Besides the openings mentioned above, the 
stove will be provided with a blow off valve to relieve the pressure and 
provide partial escape of air on changing the stove from air to gas. This 
valve may also regulate the admission of air for combustion. Numerous 
clean out holes, through which the flue dust that collects in the stove 
while it is being heated may be removed, will be placed at points most 
desirable for the purpose. 


i See Modern Methods of Burning Blast Furnace Gas by A. N. Diehl. Year 
Book of the American Iron and Steel Institute, 1915. 







144 


BLAST FURNACE 

































































STOVES 


145 


Stove Linings: Stove linings is a term that corresponds to furnace 
lining, and includes all the brick work enclosed by the shell. As in the 
case of the furnace, an expansion space of about two inches is left between 
the circular brick wall and the shell. For these linings a strong yet porous 
firebrick is required, because such brick absorbs the most heat and also 
gives it up most readily. The brick need not be very refractory, for the 
temperature in the stove is relatively low except in the combustion chamber, 
where a brick possessing fairly high refractory properties is required. The 
temperature of the hot blast is maintained at about 538° C. (1000° F.) 
which marks the lowest temperature to which the hottest part of the stove 



Fio. 21 a. Cross Section of Blast Furnace Stove. Section C C of Fig. 21. 





































































































































































































































































































































































































































































































































































































































































































146 


BLAST FURNACE 


can drop. With modern stoves, from 25 to 30% of the gas produced by 
the blast furnace is required to maintain the blast at the correct temper¬ 
ature. Of the remainder about one fifth, (12 to 20% of the whole) is used by 
the blowing engines, so that a little more than half of the total gas produced 
by the furnace is available as surplus for the generation of electrical power. 

Dust Catcher and Gas Mains: From the down-comer the gas from 
the furnace passes directly into the dust catcher. Its object, as implied 
by its name, is to clean the gas as much as possible of the flue dust blown 
over from the furnace, with which dust the gas is heavily laden. If this 
dust is not removed, in part at least, it cakes upon the walls of the combustion 
chamber and small flues of the stoves and, dropping down, necessitates frequent 
cleaning. Besides, it acts as an insulator on the brick, preventing the full 
absorption of heat. Similar conditions also prevail when the dirty gas is 
burned imder boilers. The dust catcher may be looked upon as a great 
enlargement of the flue, or down-comer. Its diameter is often 20 feet or 
more. It is brick lined, often has a dome shaped top, and a bottom in 
the shape of an inverted cone. The principles involved in its construction 
is that of greatly reduced velocity accompanied by sudden change in 
direction. By this means the dust in the gas may be reduced sufficiently 
to be used under boilers and in stoves with large flues very satisfactorily. 
From the dust catcher the gas passes through a gas main that divides 
into two branches—one to supply the stoves and one to furnish gas to the 
boilers for generating steam, which disposal will now apply to the older 
and less progressive plants only. In up-to-date plants, the gas will be 
subject to additional and more efficient treatment, after which it may be 
used in the two ways mentioned or in internal explosion engines. This 
additional cleaning of the gas is a necessity where gas engines are used, 
and it is also claimed that gas for the stoves is cleaned at a profit, since 
it eliminates the necessity of frequent cleaning of the stoves and permits 
smaller checker flues, thus increasing the heating surface of the brick. 
The matter, while past the experimental stage, is not yet fully developed 
at all plants. As representing a highly developed method of gas cleaning, 
the Duquesne works will furnish a good example. 

Arrangement of Furnaces and Cleaning Plant at Duquesne: At 

this plant there are six furnaces situated in a row, for the full length of which 
extends a large gas main, called the rough gas main. The gas from all 
these furnaces may enter this main after passing the dust catchers. From 
this main, gas may be led to any part of the plant to be used in the raw 
state, though it is primarily intended to supply the cleaning plant. The 
flow of the gas through the main is controlled by water valves. A water 
valve is a vertical cylinder with a cone-shaped bottom; in its center is a 
vertical diaphragm reaching down over half way to the base of the valve. 
Water can be admitted into the valve to a level somewhat higher than the 
lower edge of this diaphragm. With the water level below the diaphragm 
an outlet is provided so that a current of gas may be allowed to flow through; 





147 


GAS CLEANING PLANT 

£ 


when water rises high enough above the base of the diaphragm to resist 
the pressure of the gas and prevent its passage under the diaphragm, the 
valve is sealed. By means of these, any furnace can be shut off from the 
system. The gas cleaning plant consists of two divisions called the Primary 
and Secondary. The primary division receives and washes all the gas that 



Fig. 22. Diagram showing Route of Gas from Furnace through 
Gas Cleaning Plant to Boilers, Stoves and Gas Engines. 

Carnegie Steel Company, Duquesne Steel Works. 

is brought from the furnace by the rough gas mains and returns the washed 
gas to the stoves or boiler houses when desired. Phe secondary division 











































































148 


BLAST FURNACE 


receives only such gas as is intended for use in the gas engines. 

Primary Division: The primary cleaning of the gas is accomplished 
by vertical water scrubbers and fans. It reduces the dust content of the 
gas to .06 grain per cubic foot of gas under standard conditions. The 
vertical water scrubbers are the most important part of the equipment in 
respect to the amount of dust removed from the gas. There are nine of 
them, and the gas connections for them are led to their bases from the 
gas main through water-and damper-valves. These scrubbers are vertical 
steel cylinders, unlined, 77 feet 6 inches high and 12 feet in diameter, and 
are built of % inch steel plates. Gas is admitted at the base. Water is 
admitted so as to fall against the gas, and, as the currents flow in opposite 
directions, there is intimate mixture between them. The water is applied to 
the gas in the form of a spray and when falling in the interior of the 
scrubbers is like rain in that it is in small drops and thus presents the 
greatest possible surface to the gas. 

Methods of Scrubbing the Gas: Two methods of producing and 
supplying the water spray have been used at this plant. . The older method 
employed a horizontal spray pipe located in the top of the tower and rotated 
by a small electric motor. Water was supplied to it from a pipe inserted 
at the top. The falling water was prevented from striking the shell by 
a vane in the bottom of the spray pipe. Just below the spray pipe were 
12 screens set together so as to break up the water stream as it fell, but 
from that location the spray fell uninterrupted to the base, where it was 
drained out through a gas seal. In the improved form, two series of seven 
pipes each are inserted one above the other. The water is forced up through 
screens placed at six foot intervals and must then fall back through them. 
Motor-driven cut-off valves shut off the water from each pipe in turn, making 
an area of low resistance over the pipe from which water has been cut off. 
The gas rushes to this region; then water is turned on again and the gas is 
deflected. A spiral motion results, giving a larger exposure of gas area to 
cleaning water than would ordinarily result. The scrubbers use about 
6,000,000 gallons of water per 24 hours. The temperatures of the gas 
entering the scrubbers range from 300° to 600° F., and the pressure varies 
from 8 to 16 inches of water. The water enters the scrubbers at river 
temperature and at an average of 57.4° F. with a maximum of 84° F. and a 
minimum of 33° F. The dust caught in the settling basin, which is built in 
duplicate and extends from one end of the plant to the other, averages half 
to three-quarters of a standard 50-ton hopper car a day. The gas passes 
at a velocity of four feet per second up through the steel shell into a 
pipe connecting with a 10 foot 6 inch main. The gas leaves at a temperature 
varying from 96° F. to 37° F., or at an average of 68°F. The dust in the 
gas is reduced from 3.5 grains per cubic foot to .22 grain at standard 
conditions; the moisture in the gas entering the scrubbers is 34 grains per 
cubic foot and on leaving is 8.5 grains. About 25 cubic feet of gas is 
cleaned per gallon of water used. 




GAB CLEANING PLANT 


149 


The Fans: From the scrubbers, a large gas main, 10 feet 6 inches in 
diameter and about 40 feet above the ground, conveys the gas to a number 
of fans that complete the primary cleaning of the gas. The connections 
to these fans are provided with water valves. The fans are located in a 
gas cleaning building, or fan house, and are four in number. Each fan has 
a rated capacity of 84,000 cubic feet of gas per minute at 100°F. The fans 
raise the pressure of the gas to about six inches of water and thus give it 
sufficient head to pass through the entire system of stoves, boilers and 
engines; the furnace pressure alone is not sufficient to supply this head. 
The gas leaves the fans at temperatures varying from 93° F. to 35°F., or 
an average of 69° F. By introducing water at several points into the shell 
of each fan, the fans are made to serve as cleaners, and the dust content of the 
gas is reduced from .22 grain per cubic feet to .06 grain per cubic feet. 

Water Separator: From the fans, the gas passes through water 
separators. These are made of two concentric steel cylinders which stand 
in a vertical position. The outer cylinder is much larger in diameter than 
the inner one and somewhat longer, so that the gas, entering at the top 
of the outer cylinder and on a tangent, is given a downward spiral motion 
and escapes at the bottom rising through the inner pipe. In this way, 
the greater portion of the water, owing to its greater inertia, is deposited 
by the gas current. From the water separator the gas enters the clean 
gas main and is distributed to the stoves and boilers and also to the 
secondary division. 

The Secondary Division: This division furnishes gas for internal 
combustion engines, which require gas almost as free from dust as the air 
itself. It consists of four Theisen cleaners. This cleaner is a combina¬ 
tion fan and cleaner. Externally it has a form approximately like that of 
a large steel cylinder and is mounted horizontally. This outer cylinder is 
stationary and encloses a similarly shaped but smaller revolving cylinder on 
the shell of which is riveted twenty-four steel vanes. These vanes project 
12 inches from the shell of the inner cylinder and extend longitudinally in a 
slight spiral to the circumference. At the receiving end the vanes project 
beyond the end of the cylinder to form a drawing fan for receiving the gas, 
while at the delivery end they terminate in blades, attached to the same 
cylinder, that act as a booster fan for propelling the gas through the succeed¬ 
ing apparatus. Water is admitted at low pressure through six pipes half 
way up and on the side of the outer shell. This water is dashed to a spray 
by the revolving vanes, and, being propelled in a direction opposite to that 
of the gas, is thoroughly mixed with it, thus wetting the last small particles 
of dust, which must, therefore, separate with the water. This water is 
let out of the apparatus through a water seal at the bottom. The gas 
flows through the shell and out into a water separator, thence to the gas 
main leading to the gas engines. The Theisen cleaners have a rated 
capacity of 14,000 cubic feet of gas per minute at standard conditions. The 
gas leaves the Theisen at an average temperature of 64.2° F., or a maximum 





150 


BLAST FURNACE 


of 91 ° F. and a minimum of 35° F. The water enters at an average of 57.5° 
F. The dust in a cubic foot of gas is reduced from .06 grain to .009 grain. 
45.44 cubic feet of gas is cleaned per gallon of water consumed. 

SECTION VI. 

EQUIPMENT FOR HANDLING RAW AND FINISHED MATERIALS. 

The Boiler House, Power Plant, Pumping Station, Blowing Engines, 
etc. while constituting a very vital part of the blast furnace equipment 
present features of more interest to engineers than to metallurgists and 
are therefore, best omitted from this discussion. 1 

Dry Blast: About 60% by weight of all the materials entering the 
blast furnace is air. As air always contains moisture and since the decom¬ 
position of water is an endothermic reaction, the heat absorbed by the 
amount of water thus entering the furnace may be very great. It has 
been estimated that during the month of July, for instance, the average 
quantity of water, per hour, entering a furnace using 40,000 cubic feet of air 
per minute is approximately 224 gallons. That this quantity of water 
may seriously affect the operation of the furnace is now well recognized, 
and installations for drying the air have been made at a few plants. With¬ 
out discussing in detail the apparatus used, the principle employed is that 
of refrigeration. By cooling the air to a low temperature by drawing it 
over a system of pipes cooled with brine, (a solution of common salt, NaCl, 
or calcium chloride, CaCl 2 , which has a less corrosive action on the pipes), 
which in turn is cooled with liquified ammonia, the moisture is condensed 
and frozen on the pipes, leaving the air practically dry. 

Cold and Hot Blast Mains: It is still the most common practice to 
use undried air, which, compressed by the blowing engines, is forced 
normally under the high pressure of about 15 pounds per square inch through 
the cold blast main into the stoves, from which it issues highly heated; and 
passing successively through the hot blast main, the bustle pipe and the 
tuyeres, begins its work in the furnace. In this connection one or two 
apparent^ minor details of construction referring to temperature regu¬ 
lation and pressure control should be noted. Leading around the stoves 
from the cold blast main into the hot blast main is a small pipe called 
the by=pass. It provides a means of controlling the temperature of the hot 
blast. The snort valve, also located in the cold blast main, is used to 
reduce the pressure of the blast at the end of a cast while the tap-hole is 
being stopped, or to release the pressure in case of a hanging furnace. 

Appliances for Handling Ores, Coke and Stone: As was pointed 
out in Chapter III, all ore is shipped over the Lakes from May until 
December. Consequently the ore required to operate the furnaces during 
the months intervening between shipping seasons must be stored until used, 
either at the docks or at the works. This storing of ore requires a stock 

!For details on construction of the blast furnace and equipment, see Blast- 
Furnace Construction in America by J. E. Johnson, Jr., published by McGraw-Hill 
Book Company, New York. 







HANDLING RAW MATERIALS 


151 


yard with suitable provision for an ore pile, rapid means of unloading cars, 
and convenient and economical methods and appliances for handling large 
quantities of ores. For unloading the cars, car dumpers have been 
installed, while for piling and delivering the ore to the bins over the stock 
house, ore bridges are employed. The ore, arriving at the works in train 
load lots, is switched to a siding ahead of the car dumper, and the cars 
are unloaded one by one in rapid succession. A car, being pulled up an 
incline to the platform of the dumper, is bodily lifted and turned over so 
as to empty its contents into large larry cars, or into bins, if small larry 
cars are used. The dumper then resumes its former position, and the car 
is pushed off the platform by the next car of ore to an incline, down which 
the empty car moves to a car siding. Larry cars, designed for the purpose, 
carry the ore to the ore pile, where the ore bridge picks up the ore and 
dumps it in its proper place in the pile. The details of this operation will 
vary much, but the general scheme is essentially as stated. Aside from 
the mere storing of the ore other aims, while more or less incidental, must be 
kept in mind. In order to obtain uniform conditions necessary to keep the 
furnace operation under good control, it is desirable to mix the ore of each 
kind or grade as much as possible; again, the uniformity of the ore may 
be affected by dumping on large, sharply peaked piles, because dumping in 
this manner causes a separation of the coarse and the fine material, which 
always differ widely in chemical composition. For similar reasons, the 
use of ore direct from hopper cars unloaded from the trestle into the bins 
is undesirable. The ore is the only material stored, both the limestone 
and the coke being brought in as required. All up-to-date plants are 
provided with an ore trestle running out over the bins above the stock 
house. The bins are used for storing smaller amounts of ore, fuel and flux, 
which are then conveniently available for immediate use. The bins are 
large hoppers, the bottom openings of which are closed in such a way as 
to permit the withdrawal of fixed quantities of materials as desired. The 
bins for the three materials are alike except that those used for coke are 
provided with screens for removal of the ‘'fines .’’ In the most modern 
plants the open tops of the bins are covered with a heavy grid-iron grating, 
which serves the two-fold purpose of preventing accidents, resulting from 
workmen falling into the bins, and the stoppage of the chutes below, due to 
oversize pieces of material that might otherwise be dropped in. 

Stock House Equipment: Under the trestle and bins is a large space 
known as the stock house. Here are found the mechanical devices which 
have superseded the old and original method of charging by hand. r Ihe 
equipment will be different for each type of hoist. If the skip hoist is in 
use the arrangement in general will be as follows:—The skip tracks will 
extend down beneath the floor of the house far enough to permit the lowering 
of the skip beneath chutes, which lead from the floor so as to deliver the 
materials into the mouth of the skip. These materials will be delivered 
to the chute by means of a small trolley car, running on tracks that extend 




152 


BLAST FURNACE 


under the bottom openings of the bins. This car—a small hopper car— 
is provided with a scale to weigh the ore and stone as it falls into the hopper 
of the car. In this way any mixture of ores or stone desired may be 
accurately made up by weight for charging. In the bucket hoist the bucket 
itself is placed, on descending, upon the weighing car, which is transported 
by trolley or dinkey from bin to bin for the different ores required in making 
up the charge. Only the ore and stone are weighed, the coke being charged 
by volume. 

Disposal Equipment for the Iron: The old method of casting the 
metal in beds of sand has, for many reasons, been replaced by casting 
machines. Of the two types of these machines, the endless chain carrying 
a series of parallel moulds or troughs with over-lapping edges is the one 
most commonly used. In the operation of this machine, the molten metal 
from the furnace is allowed to flow into ladles, which are pulled at once 
into the casting house. Here, the metal is poured slowly into a trough 
from which it flows onto two lines of moving moulds, which have been 
previously prepared, to prevent sticking of the iron, by being either 
“limed” or “smoked.” The chains may carry the iron directly through 
a trough of water, or dump the half cooled pigs upon a second conveyor to 
be so cooled. A number of modifications of this machine are in use. 

Equipment for Slag Disposal: The greater portion of the slag 
produced cannot be used except as w^aste, so most of it will be transported 
while molten to a convenient spot and dumped. When the slag is to be 
used for certain purposes, as for making Portland cement, it is best granu¬ 
lated. This condition is produced as the slag flows from the furnace by 
allowing it to fall into a large concrete lined pit, partly filled with water 
and known as the granulating pit. By forcing a small stream of water against 
and from behind the stream of molten slag as it drops into the pit, the stream 
of slag is broken up and the fineness of the slag is increased. Merely 
allowing the slag to fall into the water is a much less effective method. 

SECTION VII. 

OPERATING THE FURNACE. 

Blowing In: Upon being completed and provided with as much of the 
equipment described above as is necessary or desired, the active career of 
the furnace is begun. In blast furnace parlance, the process of starting a 
furnace is called blowing in. It is carried out in three steps; these steps 
are drying, filling and lighting. 

Drying: Newly constructed furnaces and stoves, or new linings, must 
be carefully and thoroughly dried before being put into operation. In the 
case of a furnace fully equipped and ready to operate, the drying may be 
accomplished by either wood fires built in the hearth or by gas. The heat 
is applied very gradually, and the drying is continued for about ten days. 




OPERATION OF THE FURNACE 


153 


Filling: After the furnace is sufficiently dried, it is allowed to cool 
slightly, and then the important process of filling is begun. While different 
individuals will pursue slightly different methods, the general scheme will be 
rather uniformly carried out. Briefly stated, it consists of first placing wood 
and coke on the bottom to a height somewhat above the tuyeres, about which 
fine kindling, shavings, oily waste or any material easily ignited is piled; 
then following the wood with a large quantity of coke, mixed with enough 
lime stone to flux its ash, and gradually introducing ore with the proper 
amount of flux. Good practice requires that this initial volume of coke 
should be about half the cubical contents of the furnace. Sometimes, to 
get an easily fusible slag and a good volume of it, blast furnace slag may 
be introduced ahead of the ore. These are called the blowing-in burdens, 
and additions are made till the furnace has been filled to the stock line, 
when it is ready for lighting. 

Lighting: Starting the burning of the wood in the bottom of the 
furnace may be done in several ways. If the space in front of the tuyeres 
has been filled with light kindling wood, as is customary, oil is poured or 
sprayed in at the tuyeres until the wood is thoroughly soaked with it. Then 
with all the gas burners and valves in the gas mains and the bells closed, 
the bleeder and explosion doors are opened, a light blast is turned on and 
the wood ignited by inserting hot bars through the tuyeres. Often, instead 
of the hot bars, a wood fire is built in the stove nearest the furnace, and 
the oil is ignited by blowing sparks over with the blast. With a light 
blast on, the wood soon burns away, and the stock begins to settle, after 
which the blast pressure is gradually increased. Some furnacemen start 
off, after the fires are well caught, with a fairly high blast pressure for a 
few minutes, in order to drive the flames well in toward the center of the 
furnace and consume the wood quickly, as it is thought that a better initial 
settling of the stock is thus obtained. As soon as the stock gives signs 
of settling, the blast pressure is reduced to that normally used for the 
remainder of the blowing-in period, which is at first about 24 that used 
when the furnace is in full blast. Up to this point a great deal of gas and 
smoke escape from the furnace openings, and great care must be exercised, 
for the gases contain a high percentage of carbon monoxide, and are very 
poisonous. Great care is also required to prevent explosions, because 
mixtures of furnace gas and air in a wide range of proportions are explosive. 
Since the interstices of the stock in the furnace and all the gas mains are 
filled with air to start with, an explosive mixture may be formed any time 
soon after the lighting, and if this mixture should be ignited it might 
cause serious damage. The difficulty is generally overcome by providing 
outlets for the gas at the ends of the gas mains. These outlets are kept 
open until all the air has been expelled, which condition is indicated by 
the color and odor of the escaping gas. Both men and fires are kept 
away from these openings until it is time to use the gas and the outlets 
are closed. 



154 


BLAST FURNACE 


Heating the Bottom: Another feature connected with the lighting 
of the furnace is heating up the bottom, which is warmed by the dry¬ 
ing-out fires to only a slight degree as compared with the temperature 
required to keep the slag and iron that form in a molten state. In order to 
have the bottom at the proper temperature when slag begins to form, two 
methods are employed, both of which involve leaving an opening at the 
tapping hole so as to draw the flame downward from the tuyeres upon 
the bottom. In the first method a round tapered wood plug, three or four 
inches in diameter at the smaller end, is placed in the tap-hole and the 
space about it is packed full and tight with clay. With the rise in tem¬ 
perature due to the burning of the wood and coke in the bottom, the clay 
sets, and this plug is then removed, which permits the flame from within to 
shoot forth, thus heating up the runner outside as well as the bottom inside of 
the furnace. When slag begins to flow from the tap-hole, the opening is 
closed until time for tapping the first iron has arrived. In the second 
method, an iron pipe, about four inches in diameter, is placed in the fur¬ 
nace, before it is filled, so that one end protrudes from the tap-hole out¬ 
side of the hearth, while the other extends to the center of the furnace. 
The space about the pipe where it passes through the wall of the hearth is 
tamped with clay or ball stuff, which is also built up about the part of the 
pipe within the furnace for a foot or so from the hearth wall. When the 
furnace is lighted the gas flame is drawn to the center of the bottom to 
pour forth from the exterior end of the pipe. This pipe need not be moved 
until a fairly large flow of slag is attained, when it is drawn from the tap- 
hole, which is immediately closed, as in the case of the wooden plug. 

The heating of the stoves is another factor connected with the light¬ 
ing of the furnace. The temperature of the hot blast when the furnace is in 
full operation is 500 to 550° C. (930 to 1020° F.), and it is a great help if 
the stoves can be heated nearly to this point for the lighting of the furnace, 
especially as the furnace and filling are cold to the bottom. But this stove 
temperature can be obtained by the use of gas only, so that in the case of 
isolated furnaces where gas is not available before starting up the furnace, 
the stoves must be heated as hot as possible for the lighting by means of 
wood and coal fires. 

Tapping: At the end of ten or fifteen hours after the blast is on full, 
there will be a sufficient accumulation of slag to tap. This is done by re¬ 
moving the bott from the monkey, and pricking through the solid slag clos¬ 
ing the opening, if the cinder does not flow immediately. The bleeder is 
closed after the first cinder is tapped, as the gas can now be used in the 
stoves, and boilers or gas engines. It requires from 30 to 40 hours before much 
iron accumulates. When the iron is ready to tap, a hole is bored by means 
of a long auger or drill, electrically or otherwise operated, almost through 
the clay plug of the tapping hole. During the boring, the dust is blown 
out of the hole by a jet of compressed air. The splasher having been put 
in place, the opening is then completed by driving a long pointed bar into 
the furnace. When this bar is removed, the iron will usually flow out, at 





OPERATION OF THE FURNACE 


155 


first slowly. As the flow of iron progresses, the opening is enlarged and 
the metal flows out rapidly. The iron will then flow out through the 
runners under the skimmer to the ladles provided to receive it. During 
the flow of the metal, samples of the iron for chemical analysis and fracture 
tests are taken by collecting small spoonfuls from the main runner. The 
slag, which follows the iron near the end of the cast, is stopped by the 
skimmer, where it may be run off through a more elevated runner to the 
slag ladle or granulating pit. When the iron has almost ceased to flow 
from the tapping hole, and gases are pouring forth, the blower signals the 
engineer to reduce the blast and opens the snort valve on the cold gas 
main to relieve the pressure. Then, the iron and slag having been drained 
from the skimmer, the clay gun, hung on a crane, is swung into the 
opening, either by hand or mechanically. This gun is provided with a 
steam cylinder which operates a rammer that forces a quantity of clay 
mixed with a little coke dust into the tap hole. The clay forms a plug 
that closes the opening. This plug of clay is then backed up with more 
of the mixture, which is fed into the gun, through an opening for the 
purpose, in the form of moist balls. As soon as the hole is stoppered, 
the snort valve is closed and the furnace goes on blast till next tapping 
time—four, five or six hours afterward. 

Care of Runners: After the tapping hole has been closed, from one to 
three minutes being required, the troughs are emptied, and preparations for 
the next cast are begun. The runners are cleaned carefully of both metal 
and slag, and their inside surfaces are carefully brushed with a thick clay 
or loam slurry which, when dry, protects the trough, and prevents the 
iron from sticking to the runner. 

Sampling the Iron: Sampling pig iron is a very important part of 
every tapping. As the iron is graded by chemical analysis, care should 
be taken to secure a sample for the chemical laboratory that will be repre¬ 
sentative of the whole cast. This sample, therefore, is generally made 
up of a number of equal portions taken from the main runner at the farther 
side of the skimmer and at periods corresponding to the middle of each 
ladle of metal in the cast. These samples may be in the form of shot made 
by pouring the molten metal slowly into water or upon a cold iron plate, or 
they may be small castings made by pouring the metal into a mould. In 
addition to these laboratory tests, samples called sand tests or chill tests, 
according to the manner of casting them, are also taken. In these tests 
the iron is allowed to cool in small moulds about two inches square in cross 
section and four inches long. The moulds maybe either of sand as in “sand 
tests” or of metal, when they are called “chill tests.” When cold, the 
small casting is broken with a hammer, and from the fracture thus exposed, 
if the test has been cooled properly, the blower is able, generally, to judge 
very closely as to the quality of the iron. Chill tests of all slags are 
also taken and carefully inspected. 




156 


BLAST FURNACE 


Tapping Slag: In about two hours, the slag will have risen near the 
tuyeres, and another flush will be necessary. If the iron is tapped six 
times a day, only two flushings of slag are necessary between tappings, 
but if the tapping is on a five hour schedule three flushings will be 
required. 

Changing Stoves: The temperature of a furnace at the hearth is a 
matter of great importance, as this is one of the two main factors which 
control the quality of the iron produced. One of the means of regulating 
this temperature is by changing the slag composition, as has been suggested. 
Another way by which quicker results may be obtained is by control of 
the hot blast temperature. This may be raised or lowered by use of the 
by-pass, and can be kept high by proper manipulation of the stoves. As 
a part of the routine of blast furnace work, the tending of stoves is of im¬ 
portance. They must be kept clean and be changed regularly and at not too 
long intervals. Usually but one stove at a time is employed for heating the 
blast, and the stoves are changed once each hour. Thus, each stove is heating 
for three hours. In changing stoves the hot stove must be put on the furnace 
before the cold one is taken off. To put a stove on hot blast, the gas burner 
is racked back from the gas port, and the blow off and chimmey valves are 
closed. Then in quick succession the cold blast valve and the hot blast valve 
are opened, when the blast is free to pass through the stove, which it does 
in the direction opposite to that by which the stove was heated. The 
cold stove is now taken off, the procedure being the reverse of the above. 
The cold air valve is closed, and then quickly, the hot blast valve. To 
relieve the pressure in the stove, the blow-off valve is slowly opened, which 
permits the chimney valve to be opened. The stove is then ready for the 
gas, which is admitted by racking the burner forward. 

Charging the Furnace: The charging of the furnace is a part of the 
routine that must be done with great care and cannot be interrupted. The 
furnace tends to empty itself rapidly, and constant vigilance is necessary 
to keep the .stack full. The proportions of the materials used is a pre¬ 
determined quantity. Therefore, all the materials are carefully weighed 
before charging into the furnace. The charging is usually done in rounds. 
The basis of charging is the weight of fuel in each round. The fuel remains 
a fixed quantity, and any variations in the charge are made with the ore 
and flux. Usually the coke in the round is measured by volume and 
not weighed, but, of course, the weight of the given volume in a 
round is known. The weight of this coke unit varies at different plants, 
because it is subject to no fixed rule, the opinions of furnacemen 
differ as what it should be, and it is affected by the size of the 
furnace and other conditions. The weights most often used are 10,000, 
12,000, and 15,000 pounds. Under present conditions the weight of ore 
in the rounds will approximate twice and the limestone half the weight 
of the coke. The manner of charging the materials is also subject to 
much variation. Often it will be found that all the coke in a round 




IRREGULARITIES 


157 


will be charged, followed by the ore and limestone mixed together. To 
charge in this manner, each skip or bucket of coke is first dropped upon 
the small bell or placed over the gas seal which is lowered to allow the 
coke to fall upon the big bell. This operation is repeated until all the 
10,000, 12,000 or 15,000 pounds of coke has been dropped upon the big bell, 
which is then lowered, allowing the coke to drop into the furnace. The 
ore and stone are then charged in the same manner. To illustrate the 
variation to be expected in the manner of charging, the simple scheme 
outlined above may be compared with the following, which was once found 
in use at a certain plant. 

1 skip of ore—mixture of ores A. and B. Weighed. Small bell lowered. 

1 skip of stone and ore—mixture of stone and ore C. Weighed. Small 

bell lowered. 

1 skip of coke—not weighed. Small bell lowered. 

1 skip of coke—small bell lowered. 

Big Bell Lowered. 

1 skip of stone and ore—mixture of stone and oreC.—small bell lowered. 

1 skip of ore—mixture of ores A., B. and C.—small bell lowered. 

1 skip of coke—small bell lowered. 

1 skip of coke—small bell lowered. 

Big Bell Lowered. 

i 

Some Irregularities of Furnace Operation: The blast furnace, even 
in its highest development, is by no means the even-going, easily-regulated 
monster the casual observer may take it to be. Although furnace operations 
are under better control now than ever before, the furnaceman still refers 
to his furnace in the feminine gender, because, he knows she is a fickle 
maid capable of acting in most unexpected and astonishing ways. There¬ 
fore, a full discussion of this subject would lead to possibilities and prob¬ 
abilities almost without end. However, the subject lends itself to at least 
one positive statement. It is this: there are few situations in life where 
promptness and decision, forethought and good judgment, skill and experi¬ 
ence are more needed than about a blast furnace in times of trouble. A 
few o roubles are here enumerated. 

are due to a wedging of the stock in the upper part of the stack. 
Th i bought to be caused by carbon deposition, which may, in some 

ca more in volume than that of the ore. This deposition fills up 

thi stices of the stock, so that the gas can penetrate it only with 
din iy. When this condition occurs the stock beneath the wedged 
portion settles from that above, the blast pressure rises and the wedged 
stock finally falls. The sudden release of pressure on the gases produces 




158 


BLAST FURNACE 


a result like that of an explosion. Slips of great violence nave been known 
to tear off the top and do very serious damage. 

Scaffolding occurs near the top of the bosh. This condition is often 
due to irregularities in the working of the furnace, the following explanation 
often being suggested: If the zone of fusion is suddenly lowered, the pasty 
mass at its top tends to adhere to the encircling wall, with the result that 
an incrustation is formed which projects toward the center of the furnace. 
This mass offers obstruction both to the gases and to the descent of the 
stock. If this condition is not soon remedied, the blast gases will channel, 
perhaps on one side, in which case serious damage to the lining would 
result. Dynamite is sometimes necessary to break a scaffold. This 
condition is often referred to as hanging. 

Chimneying and Hot Spots: Chimneying is caused by the improper 
distribution of the charge with the coarser material segregating to the 
center of the furnace. The hot gases naturally seek the lines of least 
resistance, and the principal reaction is up through this more open center, 
with a corresponding slower movement of the finer and more compact 
material along the side walls. With the coarser materials segregating next 
the side walls, the more violent reactions are next the brick work, with a 
cold column in the centre, and the condition is sometimes called pillaring. 
If the latter condition becomes localized, the action of the stock and the 
hot gases soon cut away the walls adjacent to the area affected, if the 
condition continues for any length of time. Eventually, this may 
develop a hot spot, showing on the shell. By the generous use of 
water sprayed against the hot spot the furnace can sometimes be kept in 
operation for a considerable length of time after a hot spot shows. In 
either case the colder material from the inactive zone causes a cold hearth 
and poor quality of iron. 

Loss of Tuyeres and Chilled Hearth may be brought about by burning 
out the coolers due to failure of the water and by filling during a slip. Bad 
slips always throw a great deal of the molten slag up into the tuyeres, 
blowpipes and tuyere stock where it immediately solidifies, necessitating 
a shut down. The large amount of comparatively cold stock that drops 
into the hearth from a severe slip may lower the temperature of the molten 
iron and slag below the fusion point, thus producing a chill in the hearth. 
When the tuyeres are finally opened in case of a bad chill, and the furnace 
is on blast, if necessary, before the tap hole can be opened, the iron can 
be tapped through the cinder notch after the removal of the coolers. 

Uncertainties and Variables in Furnace Control: Besides the 
irregularities just mentioned which affect the furnace and occur in it, 
there are many others which may arise from outside sources, because to 
obtain uniform working of the furnace it is necessary that all the raw 




BANKING 


159 


materials, the limestone, the coke, the ore, and the air, be kept uniform, 
a feat that is manifestly impossible. Again, the furnace plant may be 
looked upon as a composite mechanism containing many vital parts, of which 
the furnace itself is but the central figure. The prolonged failure of any 
one of these parts, the boiler plant, the blowing engines, the pumping station, 
the gas mains, the water lines, or the stoves, is sufficient to close down the 
furnace. All of these things are of great interest to the furnaceman, but 
their discussion cannot be undertaken in as brief a discourse as the present 
one is intended to be. 

Banking: Whenever it becomes necessary to close down a furnace 
temporarily, it is banked. This is done by charging coke blanks, beginning 
a few hours before banking. The amount of the blanks varies with the time 
the furnace is to be off. After the blanks have been charged, the furnace 
is drained as “dry” as possible of iron and slag, the connections to the rest 
of the plant are closed, the blast is shut off, the blow pipes and the tuyeres 
are removed, and the openings are bricked up tight. The bleeders, explosion 
doors and then the bells are opened, and the gas is allowed to pass out at 
the top. The furnace may now remain inactive for several days or weeks. 
In starting up, the furnace is filled up with coke and a little ore, the ashes 
are raked out through the tuyere openings, the tuyere connections are 
made and the blast is turned on. The same precautions with regard to gas 
must be observed here as in blowing in. A week or more, depending upon 
the length of the banking peroid, may be required for the furnace to 
return to normal condition. 

Blowing Out: In blowing out, charging is merely stopped and the 
stock is allowed to settle. Streams of water are allowed to flow into the 
try holes to keep the top cool and prevent warping of the bells. As soon 
as the stock line descends near the tuyeres, the blast is taken off, the tuyeres 
are removed, and the rest of the stock is later removed with shovels. This 
done, the career of the furnace is ended. 

SECTION VIII. 

THE BLAST FURNACE BURDEN. 

Burdening the Furnace: The amounts of ore and stone charged 
per ton (or other fixed quantity) of fuel is referred to as the burden, the 
fuel or coke being constant in amount. Any increase in ore and stone above 
the normal is spoken of as a heavy burden, while the reverse of this results 
in a light burden. The regulation of the proportions of ore, flux and coke 
is called burdening. It has two objects; namely, the most efficient oper¬ 
ation of the furnace and at the same time the production of the grade of 
metal desired. The subject is of the greatest importance in the operation 
of a furnace, and is a problem that may be solved either by practical exper¬ 
ience' or by calculations based on theoretical considerations. With a 
furnace well started and on familiar materials, practical knowledge only 




160 


BLAST FURNACE 


may be required to operate successfully. But in dealing with unknown 
materials, theoretical burdening based on chemical analysis must be resorted 
to. A full discussion of these matters would make this Chapter too 
technical for the purpose it is intended. However, as illustrating the pro¬ 
blems that confront the blast furnace operator, the following will supply 
concrete examples: 

Given: A furnace with a certain capacity and raw materials of the com¬ 
position shown in the following table: 

Required: 1. To produce 1 ton (2240 lbs.) pig iron with 2000 pounds 
coke or less. 

2. To produce metal containing silicon, less than 1.25%; 
sulphur, less than .040%; manganese, as high as possible; 
carbon and phosphorus, not specified. 

To determine: 1. In what proportions the ores shall be mixed. 

2. Weight of ore mixture in the charge. 

3. Weight of flux in the charge. 


Table 27.* Analysis of Raw Materials Used in the Blast Furnace. 


ELEMENTS AND RADICALS 

Dry Basis 

Formula 

1 

OE 

2 

LES 

3 

4 

Limestone 

Coke 

% 

% 

% 

% 

% 

% 

Silica. 

Si02 

6.48 

9.04 

12.78 

5.86 

3.43 

4.40 

Iron. 

Fe 

56.80 

54.84 

52.93 

55.59 

.30 

1.35 

Manganese. 

Mn 

1.14 

1.09 

.83 

.16 

• .08 

.07 

Phosphorus. 

P 

.082 

.096 

.083 

.618 

.006 

.030 

Alumina. 

AI 2 O 3 

3.22 

2.70 

3.34 

3.63 

.86 

2.80 

Lime. 

CaO 

.11 

.18 

.25 

1.22 

51.45 

.25 

Magnesia. 

MgO 

.14 

.26 

.21 

.87 

1.66 

.15 

Fixed Carbon. 

C 






90.00 

Carbon Dioxide. 

CO 2 





41.43 

Sulphur. 

s 





.940 








Un- 

Sulphuric Anhydride. 

so 3 

.03 

.04 

.04 

.06 

.060 

deter- 








mined 

Alkalies. 

Na20- 

Trace 

Trace 

Trace 

Trace 

Trace 

Trace 


K 2 O 







Titania. 

Ti02 

.018 

.009 

.012 

.019 

Trace 

Trace 

Water, (Wet Basis). 

H 2 O 

14.06 

14.50 

15.00 

12.10 

.50 

1.50 


*N. B. The preceding table is intended to give a complete list of the 
elements and radicals which make up the solid materials entering the 
furnace, or the charge. The gases, i. e., the blast, may be looked upon 
as a mixture of oxygen and inert gases composed mainly of nitrogen. In this 
mixture the oxygen content is 20.8% by volume or 23.2% by weight. 
















































BURDEN 


161 


Outline of a Method for Solving a Burdening Problem: In a general 

way the solution of the problem is arrived at in the following manner: 
From the physical condition of the various ores and the amount of each 
on hand, their relative cost or other considerations, the furnaceman 
first decides the approximate proportions in which it is desirable to use 
the ores. From these proportions he is able to determine the average 
composition of the ore mixture in each charge, the size of which he has 
also decided upon. From this average he is able to calculate the amount 
of ore required to produce one ton of pig iron, and the weight of the impuri¬ 
ties therein. Then, since he must make one ton of iron with one net ton of 
coke, or less, he is able to arrive at the total impurities in the ore and coke 
required to produce one ton of iron. These impurities, he separates into 
acids and bases, and then combines them according to the slag ratio of 
acid to base which experience has taught is the best to produce the kind 
of iron desired. This process gives the excess acids which must be fluxed 
with limestone. From the analysis of the stone he determines the available 
base, from which the amount of limestone required to flux the excess acids 
in accordance with the accepted ratio can be found. The next thing to 
consider is the slag volume, or the amount of slag to be made per ton of 
iron, which experience has taught must be within certain limits to be con¬ 
sistent with good furnace practice. If the volume of slag is very low, its 
ability to remove sulphur from the iron may be seriously interfered with, 
while if it is very high, the fuel consumption will increase above that desir¬ 
able, because coke must be consumed to furnish the heat necessary to form 
and fuse the slag. If the slag volume falls outside the limits which the 
furnaceman's judgment from experience has set for it, he must begin all 
over again, starting with a different mixture of ores, or different limestone 
or coke. Evidently, with new materials the solution of the problem involves 
a great deal of try-work with different combinations of the materials that 
may be available. 

The Burden Sheet: During the operation of a furnace, the burden may 
be changed from time to time to meet the ever changing conditions. These 
changes are governed by observation and by the analysis of the pig iron and 
slag produced. An accurate record is kept of all changes made, and of the 
weights and analyses of all materials charged, and for purposes of record and 
of comparison between the theoretical and actual conditions, this data is all 
assembled at certain times, usually once each week, placed on a burden sheet, 
and the theoretical amounts of the various ingredients of the raw materials 
and the products are calculated. To illustrate the calculations involved, the 
following burden sheet is appended. The figures given are based on a single 
charge instead of on amounts of materials used for any given length of time, 
otherwise they represent actual conditions and show a typical charge for a 
furnace making basic iron. In studying the sheet it should be kept in mind 
that only the weights of the ores, cinder, scale, scrap, coke and stone, together 
with their analyses, and the theoretical analyses of the pig iron are given to 



Blast Furnace Burden Sheet 


162 


BLAST FURNACE 


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< 

Eh 

O 

Eh 










































































































































CHEMISTRY 


163 


begin with, and that all the other figures are supplied by calculation. Also, 
it will be observed that the analyses of the raw materials are based on these 
materials in their undried, or natural, state. 

SECTION IX. 

CHEMISTRY OF THE PROCESS 

Methods of Investigating the Reactions of the Blast Furnace: A 

question, which the non-technical reader is usually much interested in, is 
this: What changes do these numerous ingredients of the raw materials 
undergo during their passage through the furnace? Now, the reactions as 
they take place in the furnace are beyond the reach of thorough investi¬ 
gation; but from a study of the chemical properties of these elements 
and compounds under conditions similar to those existing in the furnace 
and from the chemical composition of the products, which is easily obtained 
by analysis, together with observations made in working with the furnace, 
reliable conclusions as to the reactions that must bring about the various 
transitions may be formed. Nearly all the data necessary to this study 
has already been supplied. However, the following brief review of the 
chemical properties of the elements under furnace conditions may profitably 
be made. These properties are revealed by laboratory experiments properly 
conducted under conditions approximating those of the blast furnace. 

The Functions of Oxygen and Carbon: 20.8% of the blast by volume 
is oxygen, which enters the furnace at a high temperature, about 530° C., 
and, coming in contact with hot coke, immediately reacts with carbon 
giving off heat thus: 

(1) C+0 2 =C0 2 (+97200 cal.) 

In the presence of an excess of carbon at a high temperature, C0 2 is at once 
reduced to CO, and 68040 cal. are absorbed (2) C0 2 +C=2 CO (—68040 cal.) 
The net heat, then, from (1) and (2) is29160 cal. (+97200—68040=29160 cal.) 

At moderately high temperatures the CO gas formed acts as a powerful 
reducing agent and will liberate heat at the same time, thus: 

(3) 3C0+Fe 2 0 3 =2 Fe+3C0 2 (+8520 cal.) 

—87480 cal.—195600 cal. +291600 cal. =8520 cal. 

At temperatures ranging from 250° C. to 700° C., a dull red heat, the reduc¬ 
tion of Fe 2 0 3 by CO may take place in three steps, the Fe 2 0 3 being successive¬ 
ly reduced to Fe 3 04 , FeO and finally to Fe. That the reduction of the ore 
in the blast furnace does take place in this way is shown by the fact that a 
large part (60% to 75%) of the flue dust, ejected from the top of the furnace, 
is magnetic, though only Fe20s, may have been charged. The total heat 
liberated by these three reactions would be a little more than twice and the 
total iron reduced one-half as much as that in reaction (3) for equal weights of 
CO. A very interesting reaction that takes place between Fe20a and CO at 
low temperature is (4), in which carbon is deposited and heat is liberated thus: 
(4) 2 Fe 2 0 3 + 8 CO = 7 C0 2 +4 Fe+C (+55920 cal.) 

—391200 cal.—233280 cal.+680400 cal. 



164 


BLAST FURNACE 


Carbon is not deposited with magnetite and CO reacting together, but 
it may be deposited at temperatures below 600 °C by the action of 
metallic iron upon CO, thus; Fe+CO=FeO+C. The CO2 formed in the 
preceding reactions and from the decomposition of limestone may act as 
an oxidizing agent, absorbing or giving off heat, as shown in reactions 

(5) (6) (7). 

(5) Fe + C0 2 = FeO + CO (—2340 cal.) 

—97200 cal. + 65700 cal. + 29160 cal. 

(6) 3FeO + C0 2 = Fe 3 O4 + C O (+5660 cal.) 

—197100 cal. — 97200 cal. + 270800 cal. + 29160 cal. 

(7) 3Fe + 4C0 2 = Fe 3 0 4 + 4CO (—1360 cal.) 

—388800 cal. + 270800cal. + 116640cal. 

These reactions will take place at temperatures ranging from about 350° C. 
to 800° C., and their extent will be governed by the relative amounts of 
CO2 and CO in the furnace gas, obeying, in this respect, the law of mass 
action. To be reducing the volume of CO in the gas mixture must equal 
or exceed twice the volume of the CO2. 

Carbon alone is also a reducing agent toward oxides of iron at 
low temperatures (450° C. to 700° C.), but the reduction of ore by carbon 
alone absorbs much heat as shown by the following reactions: 


(8) 

3 Fe20 3 +C 

= 

2 Fe 3 0 4 

+ 

CO 

(—16040 cal.) 


—586800 cal. 

+ 

541600 cal. 

+ 

29160 cal. 


(9) 

Fe 3 0 4 

+ 

C=3 FeO 

+ 

CO 

(—44540 cal.) 


—270800 cal. 

+ 

197100 cal. 

+ 

29160 cal. 


(10) 

FeO 

+ 

C=Fe 

+ 

CO 

(—36o40 cal.) 


—65700 cal. 



+ 

29160 cal. 



Under proper conditions the reduction of Fe 3 0 3 by solid carbon may take 
place in a direct way, thus: 

Fe 2 0 3 + C=2 Fe+3CO (—108120 cal.) 

—195600 cal. +874S0 cal. 

At very high temperatures—say around 1500°C.—carbon in large excess 
may reduce manganese, silicon and phosphorus oxides, the reactions being 
represented thus: 

(11) Mn 3 C>4+C=3 MnO+CO—Heat is absorbed. 

(12) MnO+C==Mn+CO—Heat is absorbed. 

(13) Si02+2C=Si+2 CO.—Heat is absorbed. 

(14) P2 0 5 +5C=2P+5C0—Heat is absorbed. 

Some oxygen also enters the furnace as water vapor in the blast, where the 
following endothermic reaction occurs: H20+C=CO+H2- 
The hydrogen formed may do work temporarily by reacting with iron 
oxide and reducing it thus:—(15) Fe0+H2=H20+Fe. 

But the water so formed is again decomposed as shown by the presence 
of hydrogen in blast furnace gas. Therefore, the net energy result from 
water vapor is a loss. 

In this connection it should be noticed that, since carbon is the only 



CHEMISTRY 


165 


fuel employed, the carbon-oxygen reactions must be relied upon to furnish 
the heat required in the process, and that only a few of these are heat pro¬ 
ducing. Reactions (1 )to (4) produce most of the heat absorbed by other modes 
of reduction, also that required to dry the raw materials, to decompose the 
limestone, to flux the impurities, to melt the iron and slag, and to replace 
the waste. On this accoimt they are among the most important reactions 
occurring in the furnace. 

Behavior of Nitrogen in the Furnace: Nitrogen and the other inert 
gases of the air, totalling 79.2% of the blast by volume, pass through the 
furnace, for the most part, unchanged chemically. Since they equal in 
weight about six-tenths of all the other materials entering the furnace, 
they play an important part in heat conduction, and make a source of 
unavoidable heat waste. Some nitrogen, however, may react with alkali 
carbonates and carbon to form salts of hydro-cyanic acid. 

(16) K 2 C0 3 +4 C+N 2 =2K CN+3 CO. 

This reaction explains the small amount of cyanogen, (CN)2, always 
present in blast furnace gases. 

Action of Phosphorus in the Furnace: Phosphorus enters the 
furnace with the charge in the form of phosphates. At very high tem¬ 
peratures and in the presence of coke (carbon) these compounds are com¬ 
pletely reduced, as shown in reaction (14). Phosphorus reacts with iron 
to form FesP, thus: (17) 3Fe+P=Fe3P. 

This phosphide, being soluble in iron, becomes a part of the metallic 
bath in the blast furnace. Hence, the phosphorus in the pig iron can be 
controlled only through the selection of materials. 

Disposition of Sulphur in the Furnace: Sulphur is carried into the 
furnace mainly by the coke, though small amounts are found in both the 
ore and the limestone. The greater portion contained in the coke enters 
in the form of FeS, which, when melted, alloys with the iron in the furnace; 
a smaller portion, in the form of sulphates, as CaS0 4 , enters as an impurity 
in the ore, limestone and coke, and is reduced to sulphide at a low red heat 
and in the presence of carbon. At a very high temperature and in the 
presence of a very basic slag, or CaO, and carbon, the following reaction 
may take place. (18) FeS+CaO+C=CaS+Fe+CO. Owing to lack of 
proper conditions in the blast furnace, this reaction is never complete, so 
a small portion of the sulphur remains in combination with the iron. This 
iron sulphide, being soluble in iron, becomes a part of the metal. 

Behavior of Silicon:' Silicon enters the furnace as Si02, some of 
which may be combined with bases as silicates. At temperatures of about 
1200° C., corresponding to the fusion zone in the blast furnace, the greater 
portion of this silica combines with lime, CaO, and other bases to form 
silicates, which have already been discussed under the heading of slags. 
However, at a high temperature, such as exists in the hearth of the furnace, 
and in the presence of carbon, silica is reduced, and the resultant silicon 





366 


BLAST FURNACE 


combines with the iron. (19) Si02+2C=Si+2C0. 

(19A) Fe+Si=FeSi. 

Action of Calcium and Magnesium: Calcium and Magnesium enter 
the furnace mostly as carbonates. Small portions may be in the form of 
silicates, in which CaO and MgO are combined with SiC> 2 , and may undergo 
no chemical change in the furnace. The carbonates, however, are decom¬ 
posed at temperatures above 800° C., liberating CO 2 . 

<20) CaC0 3 =Ca0+C0 2 . (21) MgC0 3 =MgO+C0 2 . 

At the proper temperature for their formation the caustic lime and magnesia 
in intimate contact with SiC >2 will both combine with it to form slags. 

Action of Aluminum: Aluminum, in the form of alumina, Al20 3 , and 
•alumina silicates, is found in ore, flux and fuel. Neither alumina nor its 
silicates are reduced under the conditions that prevail in a blast furnace. 
Al 20 3 , as already pointed out, may exert a marked influence upon the 
fluidity and fusibility of the slag. 

Action of Less Abundant Elements: Titanium, potassium, sodium, 
zinc, arsenic, copper and chromium, are elements, a few of which are present 
in very small amounts in the materials used in the Pittsburgh district. 
Titanium enters the furnace as titania, TiC> 2 , combined with some base. 
Titania is similar to silica, SiC> 2 , except that it is more difficult to reduce 
at temperatures attainable in the blast furnace, and all but traces of it, 
which is foimd in the iron, passes out with the slag. Under the con¬ 
ditions prevailing in the furnace, titanium exhibits a slight tendency to 
combine with carbon and nitrogen to form titanium cyano-nitride. This 
substance is sometimes found in the salamander on the hearths of furnaces 
being repaired. Here, it occurs in the form of small cubes that have the 
appearance of copper. The alkalies, soda and potash, are foimd in nearly 
all blast furnace slags, and when they are present in the raw materials 
to a considerable extent, they are partly volatilized and driven over 
out of the furnace with the flue gases, from which they may be separated 
with an installation of suitable apparatus. Zinc is a very troublesome 
element when present in blast furnace material. Its compounds may 
be reduced in the lower regions of the stack; but, if so, the zinc is vol¬ 
atilized, driven upward by the blast, and oxidized to zinc oxide, which 
condenses on the walls of the colder part of the flues and in time closes 
up the passages to such an extent as to seriously restrict the flow of the 
gases. Zinc oxide also tends to combine with the alumina in the fire 
brick lining of the furnace, causing the brick to expand with consequent 
evil, or even disastrous, results. Arsenic acts very much like phosphorus. 
All of its compounds are reduced, and the resultant elementary arsenic then 
combines with iron to form iron arsenide which dissolves in the metal. 
Copper compounds are readily reduced, yielding metallic copper, which 
alloys with the iron. Chromium is separated from its oxides only with 
great difficulty in the blast furnace, an exceedingly high temperature and a 
special slag being required for the reduction of its oxides. 



REACTIONS 


167 


The Reactions Within the Furnace: With these facts concerning the 
properties of the various ingredients of the raw materials in mind, the 
changes that take place in the blast furnace are easily understood. The 
accompanying chart (Fig. 23) gives a graphic representation of these changes, 
showing the relative weights and volumes of materials, the reactions and the 
temperatures at which the changes take place and the final disposition of the 
products. In studying this chart, however, one important fact should be 
kept in mind. It is this: Owing to the conditions prevailing within the fur¬ 
nace, very few, if any, of the reactions will be complete, that is, use up all 
the material at hand at the location indicated. Thus, the first reaction, 
showing the reduction of the ore to metallic iron with the deposition of carbon, 
affects only a part of the ore and gas. This condition, with but one exception 
holds for all these reactions. Even limestone, which will decompose com¬ 
pletely into lime and carbon dioxide at 1000° if given sufficient time, will often 
reach the tuyeres as calcium carbonate. The fact that iron and manganese 
oxides are not completely reduced is established by their presence in the 
slag. The one exception to this rule is phosphorus. Its compounds, down ta 
small traces, are completely reduced. 

The explanation for these statements is to be found only in a careful 
study of chemical laws in connection with the conditions prevailing in the 
furnace. Such a study reveals the fact that the reactions in the upper part 
of the stack of the furnace are subject to conflicting tendencies. Thus, 
there are in constant contact with the solid substances Fe 3 C> 4 , FeO, Fe, and C 
the gaseous substances CO and CO 2 . Of these, Fes04 and CO 2 are oxidizing 
agents. FeO and CO may act as either oxidizing or reducing agents, while 
C and Fe are reducing agents. With these substances in contact at any given 
temperature and in any given proportions as shown on the chart, the reversible 
reactions would proceed in a given direction until equilibrium should be estab¬ 
lished, and no further change would occur until either the concentration of one 
of the reacting substances or the temperature should change. Then the re¬ 
actions, subject to the law for mass action, would proceed in a direction that 
would again establish equilibrium. But the slow downward movement of the 
stock to regions of higher and higher temperatures, the presence of an excess 
of carbon and the rapid upward flow of the gases, which has the effect of giving 
a constant surplus of CO and of carrying CO 2 out of the field of action, tend 
to prevent the establishment of equilibrium, and to force the reactions 
to proceed in a direction that will result in the final reduction of the iron 
oxides, with the consequent oxidation of either the C or the CO. These 
same conditions, however, which tend to reduce the oxides of iron, prevent the 
complete oxidation of the CO to CO 2 , because the CO, passing so rapidly 
over the stock, does not have time to become wholly oxidized, and the presence 
of the reducing agents, Fe, FeO, and C, tends to oppose the formation of CO 2 . 
The escaping top gases, therefore, always show a large content of CO, much 
in excess of the CO 2 content. In modern furnaces, operating according to 
the prevailing practice with respect to coke consumption, the relative volumes 



168 


BLAST FURNACE 


150000 CU. FT 1272! LBS. = 
GASES 

♦ 

200L 05. = 26 LBS. 

DUST SiOz 


\ 

2357LBS. 


CO, 

t 

100 LBS. 



1073 

2162 

4333 


STONE 

COKE 

ORE MIX 

1 Distance from 

\ 

\ 

t 1 

j Bottom in ft. 

58 

974 

1881 

3167 732 

85 

MgCO, 

CaCO^ 

C 

Fe 2 0-5 H 2 0 


190.3 

39.2 451.2 

54.6 

4.7 20.8* 

\ 80 

Al,0, 

MnO Si Og 

FeS 

C<3lSO a CcL^P^Oq 



\ 

2.977 LBS. 
CO 

t \ 

22 LBS. |.6 LBS. 

FeO M nO 


T t 7 

2 Fe, Oa+8CO—»-4Fe + C + 7CO, 

- - t . I A 


grelo 4 + 


3Fe a Q 3 t{cO- _ 

f c * f c< 

Fe^O* ♦ 1 CO ~5FeO+|j O' 


CO 

CO, 


CO 

co^ 


FeO 


C 

CO 


Fe t 

~T~ 


jco 

l c °a 


3FeO CO g 


l 


Fe + CO^ 
CO g + C 


F g 3 P 4 fp 

FeOLCO 


2CO 


V I2CLBS.H £ 0+C 

CaCQ, 


t 


± 


l4Los.Ha+|96 Lbs.CO 
• CO, ‘ 


MgCO^—-C^Og + MgO 


CaO 

t 


Fe3 04 + C 
FeO +C 


■3F,eO.+ cb 

Fe t CO 


2 77 Lbs. 


T 


MnO + C 


♦ 


Mn+CO 


CaO^ALO.s » 5>Op 


A 


~1 

■Silicates 

A 


i 


♦ 


70 y 6 758 Lbs N, 944Lbs.H 2 3760.6Lb5.CQ 


280<SLbs C0 2 +766Lbs.C —**3574 Lbs. CO 


f2042LBS O s 76 6 LBS C ■ 
85 Lbs.H 2 0 + 56.6LBS.C- 


■ 2808LBS C0 2 
9.44 LBS Hg +.I32.23LBS. CO 


2240 LBS.PIG IRON = 2105.6LBS.Fe t 87LBS.C, 


Fig. 23. The Making of a Ton of Pig Iron, 
^es that take place therein. 


A diagram showing the raw 

















































REACTIONS 


169 


♦ 

23 LBS, 

.5 LB. 


f 

4 LBS. 
Al a 0 3 


f 

6T58LBS. 

N a 

♦ ♦ 

3.6 LBS. | LB. 

CaO MgO 


1 

606 LBS. 
H z O 
f t 

40 LBS. 1.3 LBS. 
C FeS 


Rel-ative Weights of raw Materials. 


Relative Weights of Chief Ingredients. 


Approx. Temp. 
Degrees Cent 

275 


Relative Weights of Chief Impurities. 


375 


Some Iron Sesquioxide is Reduced and Carbon Deposited. 475 


Some Iron SEsquioxiDC is Reduced to Magnetic Oxide, 550 

Some Magnetic Oxide is reduced to Ferrous Oxide. 625 

Some Ferrous Oxide is reduced to Metallic Iron. 

Some Ibqn.mav be reqxidized ^mo Carbon deposited. 700 

Some Carbon Dioxide mav be reduced b y Iron 
or Ferrous Oxide. 775 


Much of the Carbon Dioxide is p.eouced by Carbon. 


Combined Water remaining is decomposed. 


Part of the Manganous Oxide is reduced. 


Lime. Alumina, And Silica unite to form Slag 


Fusion Zone for all 5ubstances But Coke 


875 


975 


Limestone is decomposed. 

Total Lime From Ore and Stone = 576.4 Lbs. 
Carbon is absorbed bv Spqngv I ro,n. 


1075 


Reduction Of Iron Oxides is completed bv Carbon 


I 175 


1250 


1350 


1550 


1700 


2000 


Combustion Zone, (Oxygen and Water of the Air 
combine With Carbon oftheCoke to form Hydrogen 
And Carbon Monoxide.] 


Nearly all the Iron 5ulphide is converted into Calcium Sulphide, 

190.3 Lbs. Al* 0 3 , 539 . 4 LB 3 .CaO, 277 Lbs.M^ 0 t 474 LBS.CaS 

‘Tricalcium Phosphate is reduced to Iron Phosphide. _ 

Some Silica is reduced forming Iron Silicide. 

, 22.4 Lbs.S i, 2 Q. 2 LB 3 .Mn, 4 . 13 Lbs.R . 67 Lb.S _ _ Wy/x 


Ci nder Notch. 


Mas 



materials and the products of the blast furnace; their relative weights and the 



































170 


BLAST FURNACE 


of CO and CO 2 are approximately 2 to 1. In the lower part of the stack, 
the temperature is so high that CO 2 cannot exist in the presence of carbon, 
and any oxide reduced in this region results in the gasification of a proportion¬ 
ate amount of carbon. This direct reduction of oxide by carbon is the most 
inefficient mode of reduction, because it absorbs much heat, as shown by re¬ 
actions (8), (9), and (10), and robs the tuyeres of carbon needed for combus¬ 
tion. This mode of reduction, then, is one the furnaceman strives to avoid so 
far as possible. 

Tracing the Materials Through the Furnace: The ore, limestone 
and coke, upon being charged into the top of the furnace, come in contact 
with an ascending current of hot gases (temperature about 275° C.). The 
first change that takes place is the physical one of drying. The hygroscopic 
water, being first driven off and carried out of the furnace by these gases, 
is then followed by the water of crystallization. The stock, with its inter¬ 
stitial spaces filled with an ascending atmosphere containing the reducing 
gas CO, starts to descend toward the bottom of the furnace and to regions 
of higher and higher temperatures. At different levels, then, chemical 
reactions peculiar to the temperatures of these levels will occur. At first 
only the oxides of iron and carbon suffer change, and the first reaction to 
occur is number (4), in which carbon deposition takes place at a temperature 
as low as 300° C. A large part of the remaining iron oxide, in the presence 
of both C and CO, is next reduced in successive levels and temperatures as 
follows: 


3 ^ e 2O3+|Q0=?|QQ 2 +2 Fe 304 , begins at 450° C. 
Fe 304 +|^Q=|^^ +3 FeO, complete at 600° C. 
FeO +Fe, begins at 700° C. 


At about 800°C. the free iron is subject to re-oxidation by CO 2 , as are 
also the compounds FeO and Fe 3 0 4 though to a less degree, the chief action 
being represented by reaction (5). At 800° C., or a little above, the decom¬ 
position of limestone takes place, thus: CaC0 3 =Ca0-|-C02. This reaction 
is complete at 1000° C. At 900° C., carbon reduces C0 2 to CO. thus: 
C+C02=2C0, so that CO 2 does not exist below the 60 foot level. From 
this level the mixture is one of gangue, quick lime, coke, spongy iron and 
varying amounts of unreduced ore, all of which descend to the fusion zone 
with very little change, if the absorption of carbon by the iron and the 
action of carbon on the unreduced ore be excepted. At this level, which 
is located at the top of the bosh, the lime combines with some of the gangue 
and, with a little unreduced iron oxide and manganese oxide, forms a part of 
the slag. The slag, such as is already formed, and the iron, both now in 
the liquid state, trickle down through the interstices of the coke to the 



REACTIONS 


171 


hearth, where they become separated by gravity, forming these two layers; 
a lower or metallic layer containing all reduced substances and an upper 
or slag layer containing all unreduced matter. Here, since these two 
layers are in contact with each other and with carbon of the coke, which 
probably extends to the bottom of the hearth, or at least to within a few 
inches of the bottom, reactions (11), (12), (13), (14), (17), (18), and (19), 
known as hearth reactions, occur. 

Conditions Affecting the Amount of Silicon and Sulphur in the 
Metal: Reactions 13 and 18 should receive special attention here, because 
they affect the quality of metal and are subject somewhat to the control 
of the furnaceman. Number (13), Si02+2C=Si+2C0, depends upon two 
conditions, namely, temperature and basicity of slag. High temperatures 
favor the reaction, while basic conditions of the slag retard it. Reaction 
(18), FeS-)-CaO+C=CaS+Fe+CO, is subject to the former influence only. 
Therefore, the conditions which tend to raise the silicon in the iron will 
lower the sulphur content, provided the high temperature is obtained 
without the use of an excessive amount of high sulphur coke. In both 
these cases the extent of the reactions is governed by time. The longer 
the time the farther they will progress. This fact results in a difference 
in composition between the first and last metal in the same cast. Since 
the iron on the bottom of the furnace crucible is formed four or five hours 
before that on the top of the layer at the time of tapping, these reactions 
will tend to advance farther in the first than in the last iron formed under 
normal conditions. The first of the cast will, therefore, usually be found 
to contain a higher percentage of silicon and a lower percentage of sulphur 
than the last. This first iron is called “hot iron” on this account. 




172 


THE BESSEMER PROCESS 


CHAPTER VII. 

THE BESSEMER PROCESS OF MANUFACTURING STEEL. 

SECTION I. 

THE CLASSIFICATION OF FERROUS PRODUCTS. 

Introductory: In beginning this chapter it is desirable to decide the 
question as to what constitutes steel. Owing to the many varieties of iron 
now classed as steel, a concise and wholly satisfactory definition is well 
nigh impossible. Attempts have been made to restrict the usage of the 
term, but without success, because in defining any term, the name must 
be taken as it is used. Therefore, since an adequate definition of steel is 
lacking, a brief resume of the commercial products of iron may be profitable. 
In beginning this survey, it is to be borne in mind that the basis for the 
preparation of the various ferrous products is pig iron and that this 
substance, a direct product of the blast furnace, represents the crudest 
form of commercial iron. All higher grades are the products obtained by 
different methods of refinement and the degree to which this refinement 
is carried. The ferrous products may, therefore, be placed under two 
classes, namely, pig iron and refined iron. 

Pig Iron and Cast Iron: As pointed out in the preceding chapter, 
pig iron may vary, or be varied, very much in chemical composition and 
constitution. This variation gives the different grades of pig iron and 
determines the use to which the metal can be applied. On cooling, the 
crude forms first undergo a slight expansion, which is followed by a slight 
contraction. This fact makes it particularly suitable for mould casting, 
in which form it is called Cast Iron. Cast iron offers a high resistance 
to crushing, but all forms of unrefined iron are lacking in tenacity, 
elasticity and malleability. 

Malleable Cast Iron: In the second class will be found a series of 
products, which may be classified according to the initial method of refine¬ 
ment. This refinement may be brought about in two ways,—namely, one 
in which the metal remains in the solid state throughout the process and 
another in which the purification involves fusing the metal. Malleable 
cast iron is an example of the first method. Products of this class are 
obtained from crude pig iron of a certain composition chemically, which, 
upon being cast into the desired form, is subsequently subjected to a com¬ 
bined annealing and oxidizing process by which the malleability is 




WROUGHT IRON AND STEEL 


173 


developed. In carrying out the process, the clean casting is packed in iron 
oxide and subjected to a temperature of about 700° C. for three or more 
days, when it is allowed to cool in the furnace very slowly. By this treat¬ 
ment the greater portion of the combined carbon is converted into graphite 
that takes the form of very minute particles evenly distributed throughout 
the casting, and so does not have the weakening effect that flakes of graphite 
have. Some carbon, say twenty per cent of that originally present in the 
iron, is oxidized and eliminated from the metal. It is said that a slight 
reduction in the sulphur content also takes place. 

Wrought Iron: At present there are two classes of iron products 
recognized as being produced by the method of purification by fusion. To 
these are given the names of wrought iron and steel. Wrought iron, as 
indicated in the study of the blast furnace, may be produced directly from 
the ore. This method, however, has now been superseded by the indirect 
process, in which pig iron is melted in a reverberatory furnace, called a 
puddling furnace, the hearth of which is lined with iron oxide. This treat¬ 
ment results in the oxidation and consequent removal, from the metal, of 
all but small amounts of carbon, silicon, manganese, phosphorus and sulphur. 
The purification brings about a rise in the fusion temperature of the iron 
above that of the furnace, and at this point the metal is removed from the 
furnace in the form of pasty balls in which more or less slag is incorporated. 
As much as possible of this slag is at once removed by hammering or 
squeezing, after which the bloom thus produced is rolled into muck bar. 
In this form it may be converted into steel as noted below, or subjected 
to further treatment to produce merchant bar. Wrought iron is soft, 
tough and very malleable. It welds easily, and is characterized by a 
fibrous structure, due to the presence of the intermingled slag and the 
mechanical treatment it receives. Various modifications looking to 
improvement in the process of producing wrought iron have been devised. 

Steel is the term applied to all refined ferrous products not included 
under the classes described above. It is distinguished from pig iron by 
being malleable at temperatures below its melting point, from malleable 
iron by the fact that.it is initially malleable without treatment subsequent 
to being cast, and from wrought iron by the circumstance of its manufacture. 
In the case of wrought iron, the metal was in a fused state during a part 
of the purifying process only, whereas the purification of pig iron to produce 
steel takes place at a higher temperature, and the metal remains in the 
molten state throughout the period of purification. From a chemical 
analysis it is practically impossible to distinguish wrought iron from soft 
steel, but the one, being obtained in a state of complete fusion and free 
from slag, may exhibit physical properties very different from the other, 
which is obtained in a semi-fused state and retains small amounts of the 
slag incorporated with it. Between pig iron and steel, however, a marked 
difference in chemical composition as well as in physical properties is 



174 


BESSEMER PROCESS 


observed. All three substances show a wide variation in chemical com¬ 
position. The following table may be studied with profit. 


Table 28. Chemical Relations of Pig Iron, Wrought 
Iron and Plain Steel. 


PER CENT. OF 


Name 

Iron 

Carbon 

Manganese 

Sulphur 

Phosphorus 

Silicon 

Pig Iron. 

91—94 

3.50—4.50 

.50—2.50 

.018—100 

.030—1.00 

.25—3.50 

Plain 







Steel.. 

98.1—99.5 

.07—1.30 

.30—1.00 

.020—.060 

.002—.100 

.005—.50 

Wrought 
Iron. . 

99.0—99.8 

.05—.25 

(.03—10 
as cast) 

.01—10 

(.120) 

.020—.100 

.050—.20 

.02—.20 


This table would indicate that wrought iron is not the purest form of 
commercial iron, as is often asserted. However, in wrought iron part of 
the manganese, sulphur, phosphorus and silicon shown in the table above 
may be derived from the incorporated slag, in which case they would exert 
little influence upon the metal itself. 

Methods of Making Steel: Formerly it was possible to make a much 
finer distinction between wrought iron and steel than that indicated above. 
Prior to 1856, there were but two kinds of finished steel; they were known 
as shear steel and crucible, or cast, steel. Both were at that time manu¬ 
factured from blister steel made by the cementation of wrought iron. Shear 
steel was made by piling and welding blister steel bars into faggots, which 
were then forged or rolled into strips or bands suitable for cutlery. Crucible 
steel was produced by melting blister steel and scrap in graphite crucibles, 
casting the fluid metal into moulds, and then forging these small ingots 
into bars of the required size and shape. These products were distinguished 
from wrought iron by the fact that they could be hardened and tempered, 
and this property was, therefore, made the basis for a definition of steel. 
But the introduction of the Bessemer and open hearth processes, with 
their numerous grades of products, many of which can also be hardened 
and tempered and all of which are quite different from wrought iron, neces¬ 
sitated a revision of this definition for steel, because, lacking a better 
name, the term steel was applied to the products from the new processes 
also. Then, still more recently, the advent of the electric furnace added 
another variety to the ferrous metals. Finally, the cementation process 

















PRINCIPLES 


175 


has been superseded almost entirely by the crucible process, and the intro¬ 
duction of alloying elements has made a definition based on the purity of 
the metal inapplicable. It appears therefore that the only general definition 
for steel that can be offered is one based on the method of refinement. 
On this basis, then, steel is a ferrous metal, derived from pig iron or 
wrought iron, which has been subjected to a refining process by complete 
fusion. 

General Principles of the Methods of Purifying Pig Iron: From a 
commercial standpoint, the fundamental principle by which the purification 
of pig iron is effected is that of oxidation in all cases, excepting the electric 
furnace, which employs both oxidation and reduction. For the purpose of 
purifying by oxidation two substances are available. These substances are air 
and iron oxide, the application of which requires different types of apparatus. 
The twm chief methods of purification, then, represent attempts to meet 
these requirements. These methods are known as the pneumatic, or 
Bessemer, and the open hearth, or Siemens’ processes. In both, the puri¬ 
fication may be brought about by oxidation alone, in which case they are 
called acid processes, or by oxidation in conjunction with strong bases, 
such as lime, when they are designated as basic processes. By the first 
class of process, only the elements carbon, silicon and manganese are 
removed from the iron, while the second method also removes phosphorus 
and, to a limited extent, sulphur. The basic Bessemer process has been 
named after its inventors, the Thomas=GiIchrist, and the basic open 
hearth is generally spoken of as the basic. Each of the five purifying 
processes mentioned above, namely, the acid Bessemer, the basic Bessemer, 
the acid open hearth, the basic open hearth, and the electric, produces 
steel having certain peculiar properties, and with the exception of the 
electric process, each requires pig iron of a composition different from 
any of the others. Owing to the composition of iron ores available in 
this country, the pig iron produced is best adapted for treatment by the 
basic open hearth or the acid Bessemer process; hence, these are the 
leading methods employed. 


SECTION II. 

PRINCIPLES AND HISTORY OF THE BESSEMER PROCESS. 

Principles of the Process: Of all the processes for the purification 
of pig iron, the Bessemer is the simplest. Essentially, it consists of blow¬ 
ing air under pressure through a bath of molten metal contained in a 
vessel constructed of proper refractory materials, whereby a portion of 
the iron, all of the silicon and manganese, and then the carbon are suc¬ 
cessively oxidized. The first three elements, upon combining with oxygen, 
go to form a slag, while the carbon is eliminated in the form of the gases, 
carbon-monoxide, CO, and carbon dioxide, C02- As noted elsewhere, the 




176 


BESSEMER PROCESS 


V 


oxidation of these elements are exothermic reactions, from which the heat 
required to maintain the metal in the liquid state is derived. Since steel 
produced in this way, without recarburization, contains deleterious oxides 
which render it unfit for use, it is necessary to add deoxidizers to the metal 
after blowing. This fact was not realized at first, and the history of the 
process serves to emphasize its importance. 

Some Incidents Connected with the Early History of the Process: 

The history of this process also furnishes an example of the way in which 
a method is developed, and illustrates the fact that the perfecting of a 
process is seldom accomplished by one mind alone, but by many minds 
thinking toward one goal. The method was almost concurrently, but 
independently, originated by two men: one, an American named Wm. Kelly 
of Eddyville, Ky.;the other, an Englishman, the illustrious inventor, Henry 
Bessemer. Although Kelly did not apply for patents until 1857, almost 
two years after Bessemer’s English patent was granted, his application 
was allowed on grounds of priority, because he was able to prove that he 
had worked out the idea as early as 1847. In the same year that he made 
application for patents, Kelly erected a tilting converter for the Cambria 
Steel Works at Johnstown, Pa. This vessel is still preserved. Lacking 
financial means, however, Kelly was unable to perfect this invention, and 
after much litigation with the Bessemer interests, a settlement was made, 
whereby Kelly dropped out of the game. Bessemer, on the other hand, 
in addition to conceiving the idea and putting it to trial, continued his 
experiments in the face of great difficulties and many failures until he had 
brought the process to a high degree of perfection. At first Bessemer 
accidentally employed only Swedish iron, which had a low phosphorus and 
a high manganese content, and was very successful in converting it. Then, 
it having been adopted by many manufacturers, the process failed when 
applied to English irons which were high in their phosphorus and low in 
their manganese content, and prejudice and opposition to the method 
became so great among steel makers that, in order to save his process, 
Bessemer was obliged to build a steel works himself. His plant, built at 
Sheffield, began to operate in 1880. 

I m portance of Manganese: At the Sheffield works the process was used 
at first to produce high carbon steels from Swedish pig iron only, because low 
carbon steels, obtained by subjecting the metal to a full blow, were almost 
invariably hot short, even when made from the excellent Swedish iron. 
This defect was later overcome by the addition of manganese in the form 
of spiegeleisen, the beneficial effects of which were first recognized by 
R. Mushet as early as 1856. With the adoption of the use of manganese, 
mild or soft steels produced by the process came into so great demand 
that the former practice in blowing was abandoned in England, though it 
is still employed in Sweden. The first Bessemer plant in this country was 
erected in 1867. 



HISTORY 


177 


Thomas and Gilchrist: The removal of phosphorus by the use of a 
basic lining and the addition of lime to the bath was first conceived by 
Thomas, who made known the success of his scheme in 1878. In the develop¬ 
ment of this process, Thomas was assisted by his cousin, the chemist 
Gilchrist, hence the name Thomas-Gilchrist. 

• 

Other Improvements: While the process was highly developed along 
mechanical lines by Bessemer, himself, it remained for Alexander Holley, 
an American Engineer, to introduce many improvements in the erection of 
Bessemer plants. The most important of these was his invention of the 
detachable bottom, which will be described later. Another important 
invention was that of the hot metal mixer, since it furnished a ready supply 
of molten metal of fairly uniform composition, thus allowing the process 
to be operated much more rapidly and economically. This vessel, also to 
be described later, was the invention of W. R. Jones of the Carnegie 
Steel Company’s Edgar Thomson Plant at Braddock. 

Plan of Study: Before beginning a more minute description of the 
process as it is carried on with these modern improvements, it is well to 
note that the details of the operation will vary much in different plants 
as well as in different countries. The description, therefore, must be either 
very general in character, or be restricted to some one plant which will 
suffice as an example for all. For the present purpose, it is best to follow 
the latter course, and the Carnegie Steel Company’s plant at the Edgar 
Thomson Works is selected to serve as such an example. General features 
of great importance may then be introduced in connection with the dis¬ 
cussion of the various topics. At these works, the product from eleven 
modern blast furnaces is available to supply both the open hearth plant 
of fourteen 90-ton furnaces and the Bessemer plant of four converters, the 
maximum capacity of wdiich is twenty tons. 

SECTION III. 

EQUIPMENT AND ARRANGEMENT OF THE EDGAR THOMSON PLANT. 

The Converter House: The four converters are arranged in a row 
along one side of the converter building, which is located in one corner of 
the works in close proximity to the rail mills. The converters, being of 
the concentric type, tilt in two directions, in one direction for charging 
and in another for pouring. On the charging side of the vessels the building 
is erected three-story fashion. The ground floor extends under the 
converters and offers space for the removal of bottoms, slag, etc. The 
second floor, designated as the charging floor, is on a level with the 
trunnions. From this floor all molten materials are charged into the 
vessels. From the third floor, called the scrapping floor, all cold materials 
are charged. Serving the four converters on the pouring side, are two 
jib cranes for handling the steel ladles into which the metal is poured after 




178 


THE BESSEMER PLANT 



4 





Fig. 24. Cross Section of a Converter Plant. 
















































































































































EQUIPMENT 


179 


each blow. These cranes may be swung around so as to deliver the steel 
to stationary teeming tables located in front of the teeming platform which 
extends along the side of the building opposite the converters. Between 
this platform and the tables, which support the ladles during the teeming 
process, is laid a narrow gauge track, along which the ingot moulds, set 
upon small cars, are moved during and after the teeming. This motion 
in front of the platform is imparted by means of dogs attached to three 
hydraulically operated cylinders that lie between the rails of the tracks. 
All the operations of the converters and jib cranes are controlled from 
two pulpits in opposite corners of the building and above the teeming 
platform. Just back of the converter building and inter-communicating 
with it through an open side beneath the charging floor, is the bottom 
house, equipped with over-head cranes and buggies for handling bottoms. 
Here the frequent repairs to bottoms are made. As these repairs must be 
made with wet refractories, new bottoms require thorough drying before 
being put into service. For this purpose six drying ovens, each large 
enough to contain two bottoms, are provided. Built against one end of 
the converter house, like the wing of a building, is a cupola house. It also 
is inter-communicating with the converter building on its charging floor. 
In the angle formed by the cupola and bottom houses are kept the stores 
of cold pig iron, spiegel, and ferro manganese, while beyond these 
will be found a building in which is housed suitable rock crushing machines 
and Chilean mills for crushing and mixing the refractory materials used 
in making up the various mixtures required for bottoms and repairs about 
the plant. 

The Larger Accessories: The cupolas, blowing engines, mixers and 
strippers, are each separately housed and are located at various distances 
from the converter house. All these accessories play a very vital part in 
the process and in the operation of the plant, hence are deserving of special 
consideration. 

The Cupolas: In former times, when converter plants were operated 
as independent units, detached and far removed from the blast furnaces, 
cupolas were used to melt the cold pig iron preparatory to charging. At 
this plant furnaces are used only for melting the pig iron and spiegel mixtures 
employed as recarburizers. In construction a cupola is cylindrical in shape 
and resembles a miniature blast furnace. Those at Edgar Thomson Works 
are eight feet in diameter outside and some twenty feet in height, measur¬ 
ing from the mantle to the charging doors. Like the blast furnace, there 
is an opening at the bottom of the hearth for tapping out metal and another 
for slag. Above these openings are inlets for ten tuyeres, through which 
cold air, under a pressure of six to ten oimces, is blown by fans. Near 
the top are the two large openings or doors for charging, directly opposite 
each other and opening upon the charging floor. A little above these 
openings, a contraction of four or five feet in the outside diameter of the 



ISO 


BESSEMER PROCESS 


i 

shaft forms the stack, also about twenty-four feet high, for the escape 
of gases. The entire furnace rests vertically on a mantle which is 
supported by a number of columns fixed upon a firm foundation. This 
construction permits the use of the drop bottom, which facilitates the 
removal of worn-out linings, the frequent repairing required by the lower 
lining, and the rapid discharge of the stock in case of emergency. For the 
sake of economy, the lining, or wall, is made of different materials. The 
upper wall, for a distance of about four feet below the charging doors, is 
made of fire brick and is nine inches thick. Below this brick work, the 
wall is built of firestone and is gradually increased in thickness, forming a 
kind of bosh above the hearth, the walls of which are about eighteen inches 
thick. No attempt is made to cool these walls, so it is customary to 
back up the firestone of the hearth-wall with fire brick in order to safe¬ 
guard the steel shell. The shell, like that of the blast furnace, supports 
and re-enforces the masonry. It is made of steel plates, which are riveted 
together. 

Charging the Cupola: The cupola charge is composed of coke, spiegel 
and pig iron, in alternate layers of metal and coke, to the last of which 
is added sufficient limestone to flux the ash. When the orders call for steel 
with a high content of silicon, ferro-silicon is also added to the charge. 
The ratio of coke to metal varies a little. At all times the amount of fuel 
will be as small as possible, both for the sake of economy and to exclude 
sulphur and phosphorus, which are absorbed by the metal, as much as 
possible. Sulphur in the charge does not result in a rise in the sulphur 
content of the molten spiegel, but in a waste of the manganese, which reacts 
with the ferrous sulphide to form manganous sulphide, and goes off with the 
slag. Ordinarily, the coke will be about 8% and the stone about 23^% of 
the metallic charge. 

The Blast: Just outside the converter house, on the pulpit side, 
is the blowing room. Here are located three steam blowing engines of the 
compound vertical type, which create the air blast for the converters. The 
blast from these engines is delivered into a common main, through which 
it is conducted into the converter building, where it is distributed through 
a manifold to lines leading separately to the four vessels. The admission 
of air to the vessels and its pressure are nicely regulated by a system of 
valves under the control of the blower. Thus, the pressure on the main is 
maintained at about 25 pounds per square inch by means of a blow-off valve, 
which is used to regulate the pressure while the vessels are charging or 
pouring. In case some of the converters are not being operated, one or more 
of the blowing engines is stopped. By means of a second valve, operated 
from the pulpit by a screw control, a pressure of 18 to 20 pounds per 
square inch is maintained on the line leading to each vessel. Under this 
pressure the blast may be almost instantaneously admitted to or shut 
off from the vessel by means of a third valve of the butter-fly type. A 
fourth valve provides a means by which steam may be admitted to the 



EQUIPMENT 


181 


blast line as required. The limits of blast pressure to the converter are 
about 10 and 25 pounds per square inch. The lower pressure is just 
about sufficient to keep the metal out of the tuyeres in a normal charge, 
while if the higher pressure be exceeded, large amounts of metal are blown 
out of the converter. 

The Mixers: The supply of molten pig iron is obtained from two 
200-ton hot metal miners located near the blast furnaces and some three 
hundred yards from the converter mill. They are large vessels constructed 
of steel plate's riveted together to form a shell, which is lined with silica or a 
good grade of fire brick. The vessels at this plant represent the oldest type. 
They have a rectangular horizontal section and discharge the metal by 
tilting. This type has a slightly arched roof and a bottom which slopes 
from the front or pouring end toward the rear. The axis of rotation is 
located at the bottom near the center line of the vessel. Molten iron 
from the blast furnaces is conveyed to the mixer in tipping ladles, from 
which the metal is poured into the mixer through an opening in its top at 
the rear end. In the opposite end another opening, provided with a spout, 
permits the drawing off of hot metal as required by merely tilting the 
mixer, thus permitting the metal to be weighed with a fair degree of exact¬ 
ness. These mixers are not provided with gas burners, as is customary, 
for very little heat above that held by the metal is ever required to keep 
the contents molten. 

Importance of the Mixer: The hot metal mixer is almost indis¬ 
pensable to a modern Bessemer plant, or for that matter, to any steel 
making plant. Primarily the mixer serves as a storage place for the hot 
metal from the blast furnace, and in performing this function bestows great 
benefits. Thus, not only is the heat from the hot pig iron conserved, but the 
metal delivered to the vessel, or vessels, is of a more uniform composition 
than could be otherwise obtained. Again, since the capacity of the modern 
mixer permits it to contain casts from several furnaces, iron low in some 
elements may be mixed with some that is high in the same ingredients; 
and so it is possible to extend the chemical limits of the iron receivable. 
Mixers have been constructed of various shapes and sizes. Their capacities 
will range from 150 to 1200 tons, but the tendency in all modem construction 
is toward the larger size. Purification of the metal is said to take place 
to a slight extent in the mixer, sulphur being the chief impurity removed. 
The reduction in sulphur, however, is only noticeable when the manganese 
content of the iron is high. This removal is at all times so small as to be 
of minor importance. 

The Stripper: One of the most efficient, and economical inventions 
contributed to the steel business is the stripper. As its name indicates, 
it is a device whereby the moulds are pulled, or stripped, from the ingots 
after the metal has cooled sufficiently to form a solid shell on their outside 
surfaces. Those at the Edgar Thomson Works are of a late type and are 





182 


BESSEMER PROCESS 


electrically operated. A stripper of this type is in the form of a strong 
over-head crane, from which is suspended a vertical arm, provided, in place 
of a hand, with two jaws that fit over lugs cast on either side and near the 
top of the mould. Operating between the jaws is a ram, or plunger, capable 
of exerting pressure on the top of the ingot, while it is being stripped, sufficient 
to balance the pull. In stripping an ingot, the jaws engage the lugs and 
exert a powerful pull upward, while the ram, having been inserted through 
the top of the mould, holds the ingot on the stool till the mould is loosened. 
The mould is then raised high enough to clear the ingot and placed upon 
an empty car standing, ready to receive it, on a track next and parallel to 
that on which the stripped ingot stands. Electric strippers, owing to the 
fact that they are travelling, possess a decided advantage over the older 
type of hydraulically operated machines, which are stationary. 

The Casting Equipment includes the teeming ladles, ingot moulds, 
stools, and cars. The teeming ladle, which acts as a container for the 
finished steel while casting, is a large cup-shaped vessel made of steel and 
lined with a few inches of “ball stuff.” As slag is liable to spoil the ingots 
if allowed to flow into the moulds, steel cannot be poured from a vessel 
by tipping, but must be teemed from a small hole in the bottom. For 
opening and closing this hole, the vessel must be fitted with a stopper 
that can be operated from the teeming platform. This stopper consists of 
a steel rod, protected with fire-clay sleeves, to the lower end of which 
is fastened a stopperhead, made of plumbago bonded with clay, that fits 
neatly into a nozzle placed in the bottom of the ladle. The upper end of 
this stopper is fastened to a goose neck that fits over a vertical sliding 
bar attached to the outside of the ladle. This bar is provided with a lever 
by which it may be raised or lowered, causing a like movement of the 
stopper. To guard against a leaking, or ‘‘running ,’’ stopper the nozzle 
may be filled with dry sand or loam, which is held in place by a sliding 
plate on the outside. When the ladle is ready to teem, this sand is easily 
punched out of the nozzle after removing the plate. 

The Ingot Moulds into which the finished metal is teemed are made 
of cast iron and may be of almost any convenient form and size to suit 
the respective blooming mills. At these works, the standard moulds are 
about 6 feet high, have a square section of 23% inches at the bottom, with 
corners slightly rounded, and taper sufficiently to allow the mould to be 
stripped readily from the ingot. The moulds are open at both ends, and, 
when ready for teeming, rest, big end down, on heavy cast iron plates, called 
stools. The stools are mounted in twos on small cars, or buggies, which are so 
constructed that their sides form aprons that protect both the track on which 
the cars run and their own running gear from splattering by hot metal during 
the teeming of the metal from the steel ladle. The care of the moulds is 
very important, since defects here are very likely to show up in the finished 
material after rolling. Their sides must be kept smooth and clean, and 
the teeming must be done so as to avoid splattering their sides, if possible. 




CONVERTER CONSTRUCTION 


183 


After being stripped, the moulds are inspected and, if their condition is 
satisfactory, may be used again. So, after cooling to a point where the 
hand may be held against them, they are cleaned, then sprayed outside and 
on the tops with a clay wash to prevent the steel splashings from sticking, 
and marked for size of ingot required. As soon as the clay wash is dry, 
the mould is ready to receive the molten steel. Usually about seventy 
ingots may be cast in one mould before it is scrapped. 


SECTION IV. 

CONVERTER CONSTRUCTION AND REPAIRS. 

General Features Pertaining to Converters: As to the form and 
size of converters, methods of admitting the blast, and removing the steel 
after blowing, there are several possible arrangements, and converters have 
undergone many modifications. Thus, as was originally the plan, the air 
might be admitted horizontally through the wall of the vessel near the 
bottom, in which case the vessel would be of the side=bIowing type; or 
a blast of air will be forced upward through openings in the bottom of the 
vessel, to which method the term bottom blown is applied. To facilitate 
the charging of materials into the vessels and the removal of metal from 
them, converters are now always constructed so that they may be rotated 
on their shorter axis through arcs of varying size. Such converters are of 
the tilting type. The first vessels were of the fixed type, the metal being 
tapped through a hole in the wall at the bottom. In both size and shape, 
vessels still vary much. The capacity will range from 5 to 25 tons. The 
vessels at Edgar Thomson are 11 feet in diameter, outside and measured 
along their axis of rotation, and almost 18 feet long. As to form, converters 
were at first somewhat pot-shaped. Attempts to design vessels that would 
retain heat and prevent the ejection of materials has led to two general 
forms, each with its own advantages. In both forms the upper diameters 
are shortened, forming the nose of the vessel and leaving a small opening 
in the top, which forms the mouth. The body may retain the form of 
the cylinder, as in the straight=sided type, or be narrowed at the bottom 
also, in which case the body has a curved contour and somewhat resembles 
an egg in shape. The mouth may be located at the top concentric with 
the bottom and in a plane parallel to it, or it may be placed to one side, 
in which case the opening lies in a plane at an angle to the bottom and is 
then called eccentric. The vessels at Edgar Thomson Works are all of 
the bottom blown, curved body, tilting, concentric type. 

Parts of Converter: For convenience in constructing the vessel to 
allow for contraction and expansion and for making repairs later, these 
‘converters, as are all bottom blowing types, are constructed in three 
separate parts, known as the nose, the body, and the bottom. The shell 
for each of these parts is made of heavy steel plates, all firmly riveted 




184 


BESSEMER PROCESS 


together. The nose section is bolted to the body, but the bottom is held in 
place against the lower edge of the body by linked key bolts. The links of 
these key bolts fit over lugs on the body, while the key bolts themselves 
fit between lugs on the bottom, making it easy to key the two parts 
firmly together. When it is necessary to replace an old bottom with a 
new one, the keys can be very quickly knocked out or driven in with 
sledges in the hands of the workmen. The shell for the body is, itself, 
made up of three parts, known as the nose section, the journal section, and 
the shoulder section. The journal section is made up of a heavy band 
to which the two trunnions that support the vessel are attached. All 
these parts are firmly bound together by a great number of long key bolts 
attached to the shoulder and nose sections, respectively. The trunnions 
rest on bearings in a frame work which is supported by cast iron columns. 
On the end of one of the trunnions, both of which are hollow, is the 
connection, made through a packed joint, to the blast line. From capped 
openings on this same trunnion between the bearing and the vessel, a 
copper goose neck leads to the bottom of the vessel, thus forming a 
continuous passage for the blast from the main, which is stationary, to the 
wind box, which must move with the bottom of the vessel. To the other 
trunnion is attached a pinion which meshes with a toothed rack that slides 
horizontally. By means of a double acting hydraulic cylinder, the piston 
of which is connected to this rack, the vessel may be rotated through an 
arc of 270°, the pinion and rack being geared so that the vessel may be 
completely inverted for dumping slag or relining the vessel. All this 
mechanism is carefully covered to protect it from slag, dust and other dirt. 

Lining of the Converter: The lining for the shell may be composed 
of any first class silicious refractory material. At most works a highly 
silicious sandstone, known as firestone, is used, while a mixture, composed 
of about five parts crushed ganister and one part best quality fire clay and 
called ball stuff, serves as a kind of mortar. The lining varies in thickness 
from ten to sixteen inches for the different parts of the vessel, being 
thickest on those parts subject to the greatest wear. When lining a new 
vessel or relining an old one, the bottom is detached, the vessel is inverted 
and the lining is begun in the nose. The method pursued in starting the 
lining will then depend largely upon the materials available and the shape 
of the vessel. At the Edgar Thomson Works, the customary procedure is as 
follows: A wooden frame, some five feet square and with a hole in the center 
of the same shape and size as the mouth of the vessel, is laid on suitable 
cross pieces and then suspended from the vessel so as to press firmly against 
the nose and in such a position that the hole is superimposed upon the 
mouth. In this way a ledge upon which to begin the wall is formed. Upon 
this ledge is placed a three inch layer of ball stuff, which is followed by a 
course of large, flat, undressed firestone, set in on edge. All the inter-* 
stices are rammed full of wet ball stuff, so that the stones are securely 
keyed into place and the side and top present a smooth surface. Upon this 




185 


CONSTRUCTION OF THE CONVERTER 


nose wall, which is about sixteen inches thick and thirty inches high, 
the body wall is built. It consists of two courses. A thin course of split 
brick is laid next to the shell, while within this, the inner course, about 
twelve inches thick, is built up of rough blocks of firestone laid in a 
mortar of ball stuff. The stones for the top course of this wall are cut 
to shape and keyed in so as to hold the wall in place when the vessel is 
righted and also to form a smooth joint, or shoulder, against which the 
bottom is to fit. The lining is now completed by plastering the interior of 
the vessel with ball stuff, after which it is carefully and thoroughly 
dried. The coat of plaster, aside from giving a smooth surface, protects 
the stone and overcomes its tendency to spall. To prepare the vessel for 
use, the bottom is put on, the vessel is inclined, and then heated to a high 
temperature with natural gas fires in the vessel itself. In case of a 
shortage or absence of gas, coke or wood may be substituted for the gas. 
With careful patching this part of the lining may last for several weeks, 
or even months, of continuous running. 

The Bottom of the converter warrants special mention. It is the part 
of the vessel subject to the greatest wear and seldom lasts longer than 
twenty heats, when it must be removed for repairs and replaced by 
another. This change can be made with a delay of less than twenty 
minutes, and is carried out in the following manner: The bottom of the 
wind box is removed while the vessel is pouring, then as soon as the slag 
is dumped, the converter is righted, and a small but strongly built truck 
provided with a hj^draulic jack, or lift, is run beneath it. The water 
connection having been made with the hydraulic cylinder, the pressure is 
applied to the jack, which raises a small table against the bottom. In some 
plants the jack is placed beneath the track, in which case the whole truck 
is raised. The keys are next knocked out, which leaves the bottom free 
to descend with the table or the truck. The truck is then pulled into the 
bottom house, where an overhead crane picks up the bottom and carries 
it to one side. By reversing this procedure, a new bottom is soon in 
place, and the converter is ready for charging. 

Relining the Bottom: The repairing of the old bottom is immediately 
begun. What remains of the old tuyeres and filling is quickly cooled with 
water, and that on the bottom is loosened with suitable tools, when it may 
be removed from the bottom by dumping it with the crane. The removal 
of this material makes it easier to inspect the construction of the bottom. 
The shell is made of heavy steel plates riveted together in the shape of 
a shallow bowl with an open bottom. Closing this opening from within 
the bowl, is the false bottom, a flat circular casting, with openings through 
which the tuyeres may be inserted. It is a little larger in diameter than 
the opening which it closes, thus making it unnecessary to fasten it in any 
way. It supports the bottom stuff in which the tuyeres are packed. 
Covering this same opening from without is the tuyere plate, a similar 
casting containing bevelled openings into which the tuyeres fit when in 
place. This plate is prevented from making a tight joint with the bottom 





186 


BESSEMER PROCESS 


by means of the splice plates that hold the riveted plates together. Thus, 
an open space about one inch in depth is left between the tuyere plate and 
the false bottom. The plate forms the top of the wind box, the two being 
firmly bolted to each other and to the bottom with the same bolts. The 
side of this wind box is a large casting, oval in shape, and about twelve 
inches in depth. The bottom of the box is a steel plate which is firmly 
keyed to the casting to make an almost air tight joint when the vessel is 
blowing. Connecting the wind box with the interior of the bowl, are 
nineteen to twenty-one circular bevelled holes, through which the tuyeres 
are inserted. The tuyeres are cylindrical bricks, flared for a distance of 
about six inches from one end. They are about thirty inches long, seven 
inches in diameter, and each one contains about twelve holes, one-half inch 
in diameter and extending longitudinally. To place a tuyere, the flare is 
covered with a mortar, composed of fire clay and Portland cement, and 
the tuyere is inserted upward through the opening in the bottom, where 
it is held in place with clamps until the filling has been put in. When all 
the tuyeres have been thus placed in position, the top of each is covered 
with a metal plate to keep dirt out of the tubes, some bottom stuff 
is placed on the bottom in the space around the tuyeres, and on this 
large tiles are set in as reinforcement to the tuyeres. The space remaining 
about the tuyeres and brick is then tamped full with more of the bottom 
stuff, which is a moist mixture composed of 28 parts crushed ganister, 12 
parts blue fire clay, 3 parts ground brick bats, 3 parts old bottom stuff 
and 4 parts coke dust. The bottom is then pushed into a drying oven, 
fired with coke oven gas, and carefully dried, then finally baked for several 
hours. The time required to dry and bake a bottom properly is about 
forty-eight hours, though bottoms will often be used at the end of thirty- 
six hours. Upon being required for use, it is withdrawn from the oven, 
and a heavy layer of a stiff clay mixture is placed around the upper edge to 
form a tight joint with the shoulder of the vessel when the bottom is in 
place. The mortar is then sprinkled heavily with coke dust, after which 
the bottom is put into service as previously described. The function of 
the coke dust is to prevent the bottom from cementing itself to the 
shoulder joint. When in service the position of the bottom is such that 
the long axis of the oval wind box is parallel to the axis of rotation of the 
vessel. The advantage of this shape is obvious, for it is easily seen that 
with the wind box in this position a greater volume of metal may be held in 
the vessel while in the horizontal position without filling the tuyeres than 
would be possible with a round box, which is the form used on eccentric 
vessels. The double bottom, mentioned above, is also of great advantage. 
Since the space between the upper and lower plates connects with the outside, 
it not only gives warning of a worn out tuyere, but also prevents the wind 
box from being filled with hot metal in case of a break out. When a 
tuyere becomes defective or badly and dangerously worn during a blow, 
it may be plugged by turning the vessel down, removing the wind box lid, 
and stopping its openings with clay. 




PURIFYING THE METAL 


187 


SECTION V. 

THE CONVERTER IN OPERATION—PURIFYING THE METAL. 

Charging the Vessel: With the bottom fastened in place and the 
vessel at the proper temperature, it is ready for the charge. The charging 
is a matter of much importance. Besides being a factor in determining 
the composition or grade of steel produced with respect to phosphorus and 
sulphur, it also offers a means of controlling the temperature during the 
blow. It must always be predetermined by the blower, who has charge 
of the blow. In acid practice the charge consists of molten pig iron, 
to which is added cold pig iron or steel scrap in amounts sufficient to meet 
the heat requirements of the blow. As the only source of heat is the 
oxidation of the iron, silicon, manganese and carbon, the composition of 
the pig iron is important, and the blower must be kept informed in advance 
as to the composition of the iron. In operating a hot vessel on hot iron 
there is much more heat generated than is required to keep the metal 
molten, in which case the temperature may be kept under control by 
charging steel scrap. Scrap may be added to the heat at any time during 
the first part of the blow. The addition of scrap also has the advantage 
of increasing the output. In beginning on a new lining or a new bottom, 
or after a delay, the vessel will be cold and will, itself, absorb much heat, 
which condition precludes the use of cold materials in the charge. In an 
attempt to lessen the loss of iron through oxidation and shorten the time 
of a blow, roll scale or other oxides of iron are often charged. Such additions 
may reduce the blowing period by about one-third, and are made regularly 
at some plants, but this is not the practice at Edgar Thomson. On making 
a steel that requires a high sulphur content, like screw steel, the required 
amount of this element, in the form of pyrite, may be added along with 
the molten metal. The blower, having been informed as to the require¬ 
ments of the rolling mills, decides upon the charge best suited to the con¬ 
ditions, then sends an order to the mixer for a certain weight of pig iron. 
At these works this amount will vary from 30,000 to 36,000 pounds. The 
molten iron is weighed at the mixer as it is poured into the ladle, the truck 
of which sets on a scale platform. Some coke breeze is then thrown upon 
the molten metal to keep it from skulling the ladle, wffien it is taken by 
a dinkey to the charging floor of the converter. Here, the vessel is turned 
down, to a horizontal position, so as to bring the tuyeres well above the 
bath, and the molten iron is poured into the mouth of the vessel by slowly 
tipping the ladle. The scrap is added from the scrapping floor shortly after 
the vessel is brought to the vertical position. 

The Blow: Immediately after the vessel has received the charge of 
molten metal, the blast, under a pressure sufficient to prevent the metal 
from flowing into the tuyeres and also force the air through the liquid, is 
turned on, and the vessel is racked to the vertical position. With this act 
the air of the blast is forced to pass up through the molten mass, and 
chemical action between the oxygen of the air and the various ingredients 




188 


BESSEMER PROCESS 


of the metal immediately begins. This oxidation takes place in successive 
stages, each of which, provided the blow is a normal one, produces its 
own peculiar effect in the metal and upon the kind of matter ejected from 
the mouth of the vessel. Their order, therefore, may be followed by the 
naked eye or through colored glasses. As the vessel is righted a shower 
of sparks is emitted from its mouth. Then a stream of dense brown fumes 
pours forth, to be succeeded shortly by a dull red, short, pointed flame 
that protrudes from the mouth of the vessel. This action occupies but 
five or six minutes, when this flame is gradually replaced by a short luminous 
one that plays about the mouth. This flame soon begins to increase, both 
in length and luminosity, until it has reached a maximum length of thirty 
feet or more, which it maintains steadily for about eight minutes. During 
this period, known as the boil, a dull roaring coming from the vessel may be 
heard. This noise is caused by the violent agitation of the bath by the 
blast and the rapid generation of carbon monoxide gas within it. Just 
before the end of the blow, the flame begins to drop,or “die,” that is, it suddenly 
becomes less luminous, giving an effect similar to that to be expected if a 
smoked glass or a cloud were placed between it and the eye; and if it is being 
observed through blue glasses, purple streaks are visible in it. If the blow 
should be continued, this flame would disappear entirely, but the metal is 
always poured before this point is reached. Thus, the entire time required 
to convert fifteen to eighteen tons of pig iron into steel is only about fifteen 
minutes. 

Controlling the Blow: The appearance of the flame just described 
serves as an index to the change going on in the vessel, and so is very 
important to the blower, upon whom rests the responsibility for the proper 
operation of the vessel. He is also held accountable for the quality of 
the steel he produces. He has an assistant who turns the vessel for charging 
and pouring and operates the ladle crane, but the control of the process 
is in the hands of the blower himself. He must decide the best proportions of 
hot metal and scrap to use, regulate the temperature, determine the time 
for turning down and over-see the recarburizing of the blown metal. As 
to the kind of recarburizer and the amount to use per ton of steel, he receives 
instructions from his superintendent’s office. Factors that enter into the 
making up of the charge have already been explained. The importance of 
a high temperature was also alluded to as necessary to keep the bath molten. 
In this connection it remains to be pointed out that temperature is an 
important factor in controlling the blow, and so exerts an influence on the 
quality of the product. As it is impossible to regulate the charge so as 
to meet all the variations in the conditions, other means of regulating 
the temperature must be resorted to during the blow itself. To raise the 
temperature after a blow is in progress, the vessel may be turned so as 
to expose a few tuyeres above the metal. The combustion of the carbon 
monoxide gas over the bath generates heat, which raises the temperature 
of the vessel and consequently of the metal also. This method wastes 
some metal, as iron is excessively oxidized. Ferro silicon is also used for 




PURIFYING METAL 


189 


this purpose, the oxidation of the silicon being the source of heat in this 
case. Either method is expensive and should be avoided. With rapid 
working, and with iron of proper grade, cold heats are the exception, 
occurring mainly on new linings or in the first blow on a new bottom. To 
lower the temperature is a much easier matter. The vessel may be tilted 
and allowed to cool by radiation, or cold metal in the form of steel scrap 
may be added, if the heat is not too far advanced. A more convenient 
method is that of introducing steam with the blast, and as it is very con¬ 
venient, it is often employed. The water coming in contact with the 
highly heated metal is decomposed according to the following reaction: 
H20+Fe=Fe0+H2. Steam thus introduced is not very efficient because 
the oxidation due to air is not retarded and very little, if any, heat can be 
absorbed. However, less heat is generated in oxidizing iron with water than 
with air, besides, steam is easily controlled, is always at hand, and can be 
introduced in varying amounts without delay to the blow or turning the 
vessel. The blower will, then, keep close watch on the flame, and introduce 
steam during the blow as often as required to hold the temperature at the 
proper level. The speed of the blow, and, indirectly, the temperature, may 
be controlled to a limited extent, also, by varying the blast pressure. In 
this connection it should be stated that there are so many variables con¬ 
nected with the operations that no uniform method can be established. 
Even with metal of uniform composition and other conditions apparently 
alike, two consecutive heats made to the same specification will seldom 
require the same manipulation. Thus, the success of the entire operation 
depends upon the judgment of the blower. 

The End of the Blow: Owing to the rapidity of the reactions and other 
peculiar conditions, the composition of the steel cannot be well regulated by 
stopping the blow. While it is possible to blow a heat to approximately any 
carbon content desired, the method is not practiced in America, because it 
slows down the operation too much. It is much cheaper and surer, therefore, 
to blow full, and add both carbon and manganese with the recarburizer. 
This is the practice at Edgar Thomson. At these works, if the blow 
is stopped at the first indication of the drop of the flame, it is said to 
be turned down young; if continued till the drop is pronounced, the blow is 
full. In either case the silicon will have been completely eliminated, while 
only small amounts of manganese and carbon will remain. The residual 
manganese may be as high as .06 or .08%, depending upon the extent of the 
blow and the percentage in the pig iron. If the blow is turned down young, 
.08% to .10% carbon will remain, while in a full blow this amount is 
decreased to .03 or .04%. The percentage of phosphorus and sulphur is 
slightly higher than in the original pig iron, owing to a loss in weight due 
to oxidation and elimination of the silicon, carbon, manganese and part of 
the iron, and also to the ejection of metallic iron from the vessel. The 
total loss will amount to something between 8% and 10% of the charge, 
nearly half of which is oxide of iron and manganese which can be recovered 
by using the slag in the blast furnace. 





190 


BESSEMER PROCESS 


SECTION VI. 

FINISHING OPERATIONS—CONVERTING THE PURIFIED METAL INTO STEEL. 

Deoxidation and Recarburization must always immediately follow 
the blow. At Edgar Thomson this is done in the ladle as the metal is being 
poured, though at certain other plants some of the additions are made in 
the vessel. In general the objects sought are: 1st., control of the carbon 
content; 2d., deoxidation of the steel; and 3d., introduction of elements, 
such as manganese, to improve the quality of the steel. The following 
table shows the difference in the analysis of steel before and after recar¬ 
burizing, and partly illustrates the many grades produced. 


Table 29. Showing Chemical Relation of Purified Metal to 

Different Grades of Steel. 


Kind of 
Steel 

Per Cent. 
Carbon 

Per Cent. 
Manganese 

Per Cent. 
Sulphur 

Per Cent. 
Phosphorus 

As Blown.. . 

.03 to .10 

Trace to .06 

.03 to .06 

.08 to .100 

Skelp. 

Not over .08 

.30 to .40 

Not over .06 

Not over .100 

Sheet Bar. . 

“ “ .10 

.30 to .50 

“ “ .06 

“ “ .100 

Screw Steel. 

“ “ .08 

.60 to .80 

Not under .0S5 

“ “ .100 

Special 

Billet Steel 

.25 to .30 

.40 to .50 

Not over .085 

“ .100 

Light Splice 
Bar. 

.08 to .10 

.35 to .60 

“ “ .06 

“ .100 

Rail Steel. . 

.30 to .50 

.70 to 1.10 

“ .06 

“ “ .100 


Needless to say, the different grades of steel require different methods 
of recarburizing to meet the requirements, which fact calls for different 
recarburizers. The various recarburizers and deoxidizers most commonly 
employed are ferro manganese, spiegel, anthracite coal, ferro-silicon, 
and pig iron, analyses of representative samples of which are given in the 
subjoined table. 


Table 30. Analyses of Representative Samples of Deoxidizers 

and Recarburizers. 



Per Cent. 
Iron 

Per Cent. 
Carbon 

Per Cent. 
Manga¬ 
nese 

Per Cent. 
Sulphur 

Per Cent. 
Phos¬ 
phorus 

Per Cent. 
Silicon 

Per Cent. 
Ash 

Ferro Manganese.. 

11.95 

6.50 

80.40 

Trace 

.160 

1.00 


Spiegel. 

73.20 

5.00 

20.40 

«t 

.100 

1.10 


Ferro-Silicon. 

86.70 

2.00 

.50 

.050 

.080 

10.60 


Pig Iron. 

93.05 

4.50 

.67 

.047 

.088 

1.67 


Anthracite Coal. . . 


85.50* 


.... 

.... 


4.50 


♦Fixed carbon only 














































FINISHING THE BLOW 


191 


Loss of Recarburizer and Deoxidizer: In adding the recarburizers, 
a loss always takes place, for which an allowance must be made. The 
amount of this loss is fairly uniform under similar conditions, and is deter¬ 
mined by experience. In the case of manganese it amounts to about 20% 
of the manganese added for full blown heats, in which the per cent, of 
manganese does not exceed .60. The loss is somewhat less, not over 15%, 
if the blow is stopped young. The loss varies, also, with the amount of 
manganese added, increasing rapidly as the per cent, in the steel is raised 
above .60. Similar data is required in using ferro-silicon and anthracite 
coal, the loss of carbon in using the latter being about 50% of the total 
amount added. 

Examples of Recarburizing: Some simple examples of recarburizing 
will illustrate the methods employed. 1. Suppose it is required to 
produce a soft steel, such as the skelp shown in the table above. The 
metal will be given a full blow to reduce the carbon content to about .04%, 
and hot ferro manganese will be added in sufficient quantity to raise the 
per cent, of this element to .40. A simple calculation, if proper allowance 
is made for both residual manganese and manganese lost, will show that 
this amount of ferro will raise the per cent, of carbon to .08. 2. In the 
case of a medium soft steel, say .20% to .25% C., .40% to .50% Mn., the 
recarburization after a full blow may be made with molten spiegel mixture 
containing about 12% Mn. and 5% C., or, as it is difficult to handle and 
weigh small amounts of molten metal, coal and ferro-manganese are more 
often used. In the latter case, the blow may be turned down yoimg. 3. 
In the case of a rail heat the blow is turned clown young, and recarburized 
with molten spiegel mixture. Molten pig iron and ferro manganese could 
also be used, but this is not the practice at the Edgar Thomson Bessemer 
plant. At this plant the cupola charge for the spiegel mixture used to 
recarburize rail heats consists of spiegel, ferro silicon, and pig iron, in 
proportion to produce a mixture containing 12% Mn., 4.50% C., and 1.50% 
Si. For determining the quantity of deoxidizer and recarburizer to add, 
the blower is provided with a set of factors, one for each grade of steel 
produced, the numerical values of which are fixed by experience. Thus, 
for sheet bar the factor giving the amoimt of 80% ferro manganese to add, 
is .0045, but for skelp it is .0055 because this steel is blown very full. 
Similarly, factors for finishing rail steel with spiegel are given. 

Ladle Reaction: The addition of the recarburizer is usually followed 
by a violent boiling of the metal in the ladle, causing much slag to be 
thrown out over the sides. This is often referred to as the spiegel reaction 
or ladle reaction. With the addition of the recarburizer, precautions 
will be taken to mix it thoroughly with the metal. At Edgar Thomson 
this mixing is accomplished in the case of rail heats by using molten 




192 


BESSEMER PROCESS 


spiegel and pouring it into the ladle with the metal from the vessel, 
and in the case of soft steels by poling the metal in the ladle. 

Teeming: The history of the heat may now be resumed. Soon after 
the recarburizer has been added, the pouring of the metal will have been 
completed. The converter is then inverted, and the slag which did not 
flow out with the metal is dumped upon a small flat car beneath the vessel, 
which is then ready for the next charge. While this is going on, the steel 
has become quieter in the ladle and has been raised to the proper level 
by the steel crane, which then transfers it to the teeming table in front 
of the pouring platform. Here the teeming hole in the bottom of the ladle 
is opened by removing the small plate and digging out the sand, when 
the metal may be allowed to flow at will by raising and lowering the stopper 
lever. The metal is now teemed, consecutively, into four ingot moulds, 
which have been prepared as previously described. As each mould is filled 
to the mark, the next is moved under the nozzle by means of the “dog,” 
hydraulically operated and provided for the purpose. During the teeming 
of each ingot of soft or medium soft steel, small pieces, about four ounces in all, 
of aluminum may be added, as the judgment of the teemer directs, to assist 
in further deoxidizing the steel. This metal will always be added if the 
steel is very wild, which condition is often.found in soft steel made by 
this process. After all the steel has been teemed into the moulds, the 
little train is pushed along the track to the end of the teeming platform, 
where the ingots are allowed to cool. If the ingots show a tendency to 
grow in the moulds, the tops may be sprayed with water, and heavy caps 
of cold iron will be placed on them. This treatment is intended to chill the top 
and stop the growing, which invariably increases the number and size of the 
blow holes and pipe in the top of the ingot. Growing is peculiar to soft 
steels; rail heats seldom exhibit this tendency. When the ingots have 
cooled sufficiently to form a thick, strong shell on the outside, they are 
taken to the stripper, where the moulds are at once removed. This done, 
they are ready for the soaking pits, which are more properly treated under 
rolling mills. 

Sampling the Steel for Chemical Analyses: A sample for chemical 
analysis is taken during the teeming of each heat. This matter is of much 
importance, and has received the attention it deserves. The sample is 
obtained when half of the ladle of steel has been teemed by holding a large 
steel spoon beneath the nozzle and allowing a small stream of the metal 
to flow therein until the spoon is full. This metal is then poured from the 
spoon into a specially constructed mould where it is allowed to cool or set, 
after which it is stamped with the heat number and is then taken to the 
chemical laboratory for analysis. Everything has been done to insure 
this sample is truly representative of the whole heat, which is seldom true 
of samples taken in other ways. 



CHEMISTRY OF 


193 


SECTION VII. 

CHEMISTRY OF THE PROCESS. 

The Order of Elimination of the Elements: As previously indicated, 
the heat required for the process is generated by the oxidation of the iron 
and the metalloids, silicon, manganese, and carbon. An examination of 
the blow will show that, during the first period, the oxygen of the blast 
attacks first the iron, then, both directly and indirectly, as will be explained 
shortly, the silicon and manganese, producing exothermic reactions which 
rapidly increase the temperature of the bath. The converter gases during 
this period are mainly nitrogen with some carbon dioxide and traces 
of oxygen and hydrogen. These reactions produce no flame, since all the 
products of the oxidation are solids, but with the rise in temperature, 
carbon begins to be oxidized to carbon monoxide, which will burn at the 
mouth of the vessel to carbon dioxide and produce a flame outside the 
vessel. So, the heat generated by combustion of the CO to C02is wasted. 
The rapid generation of CO in the metal produces the “boil,” and the 
increasing speeds at which the formation of this gas takes place causes 
the flame to grow to a maximum size and finally subside with the elimi¬ 
nation of the carbon. The escaping gases during this period consist mainly 
of nitrogen and carbon-monoxide with small percentages of carbon dioxide 
and traces of hydrogen. Thus, at no time during the blow, except for a 
short period at the beginning, does any but traces of the oxygen of the air 
escape from the bath uncombined, though the layer of metal is but some 
twenty inches thick, and the volume of the blast is more than 6000 cubic feet 
per minute. This fact is not surprising, if it is remembered that the temper¬ 
ature of the bath from the first is much above the kindling temperature 
for any element in the bath, and that the blast is delivered by the tuyeres 
almost in the form of a spray. Under these conditions, the combination 
of these elements with oxygen must be almost instantaneous, resulting in 
all the oxygen being consumed at the mouth of the tuyere. Concerning 
the brownish fumes ejected by the converter, especially at the beginning 
of a blow, various suppositions have been advanced to account for them. 
It has been suggested that they may be volatile compounds of iron and 
manganese with carbon, which, upon coming in contact with the air at the 
mouth of the vessel, are immediately oxidized, the metallic oxides producing 
the brown color. Analysis of deposits made by this fume have been made, 
and they are found to be composed roughly of one part ferrous oxide, two parts 
silica and three parts manganese oxide. Manganese is volatile at a compara¬ 
tively low temperature, which fact may account for a part of the fume, 
but with respect to iron and silicon or silica, the most plausible explanation 
is that they are carried out mechanically in a finely divided state by the 
blast. 

The Laws and Conditions Governing the Reactions in the Con¬ 
verter: A review of the laws of chemical action and of the conditions of 




194 


BESSEMER PROCESS 


the blow will render an explanation of the changes that take place to bring 
about the results enumerated above very easily understood. If reference 
be made to the laws controlling chemical action in Chapter I., it will be 
found that,under normal conditions of blowing metal, only two are applicable 
to the matter under consideration. One of these, the law of mass action, 
states, in effect, that the rate or speed of a chemical reaction may be 
increased by increasing the active masses, or amounts, of the reacting 
substances; and the other law says that when chemical reactions take 
place without the aid of heat supplied from an external source, those sub¬ 
stances which have the greatest heats of formation, that is, those that 
give off the most energy, will tend to form. As to the conditions, these 
can be very briefly and simply stated. Thej' - are, that at the beginning of 
the blow the bath represents a solution of approximately 4 parts carbon, 
1.5 parts silicon, 1 part manganese, .1 part phosphorus and .05 parts sulphur 
in 93.35 parts iron at a temperature that is several degrees, say 100°, above 
the fusion point of the mixture; but this temperature is rapidly raised 
during the first part of the blow. The phosphorus and sulphur are not 
affected, so they need not be considered, but the elimination of the other 
impurities presents an interesting study. 

Reactions of the First Period: Chemical knowledge does not tolerate 
the idea that these impurities are oxidized by the action of oxygen directly, 
but indicates that the reactions occurring at the beginning of the blow are 
governed by the law of mass action. According to this law, iron, by far 
the most abundant element present, is first oxidized almost to the entire 
exclusion of the other three elements. This reaction, which liberates a 
large amount of heat, is represented thus: 

(1) 2 Fe+0 2 =2 FeO (+131400 cal.) 

2 (65700 calA 

With the oxidation of the iron to FeO, this oxide, being miscible with the 
metal, is distributed throughout the bath, and the oxidation of the 
silicon and manganese takes place in the order of the heats of formation 
of their oxides, as shown in the following reactions: 

(2) 2 FeO +Si=Si0 2 +2Fe (+64600 cal.) 

Heats of formation:—2(65700 cal.) + (196000 cal.) 

(3) FeO+Mn=MnO+Fe (+25200 cal.) 

Heats of formation:—65700 cal. +90900 cal. 

With the oxidation of silicon and manganese, a slag is immediately formed 
by the combination of silica with the excess FeO and the MnO according 
to the following: 

(4) FeO + Si0 2 = FeO.Si0 2 (+9300 cal.) 

Heats of formation:—65700 cal.—196000 cal. +271000 cal. 

(5) MnO + Si0 2 = MnO.Si0 2 (+5400 cal.) 

Heats of formation:—90900 cal.—196000 cal. +292300 cal. 




CHEMISTRY OF THE PROCESS 


195 


In comparing the ratio of acids to bases as determined by actual analysis 
with ratios calculated from formulas, evidence is obtained that the slag 
is made up, in part at least, of trisilicates, in which case these reactions 
would be represented thus: 

(4 A) 2 FeO+3 Si0 2 ==(Fe0) 2 -(Si0 2 )3 

(5 A) 2 MnO+3 Si0 2 =(Mn0) 2 -.(Si0 2 ) 3 

This slag, itself a solution of the two silicates thus formed, will dissolve 
some of the FeO, and being mixed with metal by the violent agitation of 
the bath, will also help to oxidize the impurities. Reactions (1) and (4) 
also account for the rapid wearing away of the bottom. This period is 
then preeminently one of slag formation. Some carbon, especially 
toward the end of the period, however, may be oxidized directly to CO 
and then to C0 2 by the FeO, thus: 

(6) 2C+0 2 = 2 CO +(58320 cal.) 

2(29160) cal. 

(7) FeO +CO =Fe+C0 2 (+2340 cal.) 

—65700 cal.—29160 cal.+97200 cal. 

These reactions account for the presence of both C0 2 and CO in converter 
gases during the first part of the blow. At the beginning of the blow, CO 
is subject to reduction by both silicon and manganese, especially if the 
iron contains a high per cent, of these elements. 

(8) 2 C0+Si=Si0 2 +2C (+137680 cal.) 

—2(29160) cal.+ 196000 cal. 

(9) CO + Mn=MnO+C (+61740 cal.) 

—29160 cal. + 90900 cal. 

Reactions of Second Period: With the elimination of silicon and 
manganese, reaction (8) and (9) cannot take place. Furthermore, the rise 
in temperature brings about reaction (10) or (10A). 

(10) FeO +C=Fe+CO (—36540 cal.), 

—65700 cal. +29160 cal. 

(10A) FeO+Fe 3 C=4Fe + CO (—45000 cal.) 

—65700 cal.—8460 cal. +29160 cal. 

These reactions, in conjunction with reaction (6), rapidly burn out the 
remaining carbon. According to the law involving heats of formation, these 
reactions should not take place, and it becomes necessary to explain certain 
apparent exceptions. At ordinary temperatures the law has no exceptions, 
but at elevated temperatures it holds true through certain ranges of tem¬ 
perature only, so that, as the temperature in any particular case is raised, a 
point, which may be called the critical temperature, is reached, where the 
energy supplied from the external source overbalances that absorbed by the 
reaction. The law then becomes reversed, and the reaction proceeds in a 
direction that will absorb the excess heat. This fact suggests the possi¬ 
bility that with hot iron, that is, iron high in silicon, which is also initially 



196 


BESSEMER PROCESS 


at a very high temperature, it might be possible to eliminate the carbon 
before the silicon and manganese could be oxidized, and the testimony of 
the older and more experienced operators of converters is to the effect that 
just such a result as this has often occurred when the conditions noted 
were present. Furthermore, in the elimination of the carbon, the law 
of mass action here becomes prominent again, for with the elimination of 
the silicon and manganese the active mass of the ferrous oxide rapidly 
increases until a second equilibrium is established, this time with carbon. 
The reaction is also probably influenced by the volatility of the carbon 
monoxide, one of the products of the reaction. Comparatively little heat 
is available in the bath during this period. The net heat generated is the 
difference between the heat of formation of FeO (65700 cal.) and that 
absorbed in reaction (10) (36540 cal), or 29160 cal. which is the heat of 
formation for CO. The carbon reaction occurs concurrently with the 
phenomenon commonly spoken of as the boil. There is, during this period, 
very little, if any, iron oxidized above that required to eliminate the carbon, 
so each volume or molecule of oxygen in the blast will produce two volumes 
or molecules of CO. The converter gases, therefore, show a high content 
of CO, very little CO 2 and a marked decrease in N 2 . The phosphorus 
and sulphur suffer no oxidation from the action of FeO until all but traces 
of carbon is eliminated, and then only in the presence and under the 
influence of a strong base, such as lime. If the loss in weight in the bath 
be taken as 10%, then steel made from iron containing .045% sulphur and 
.089% phosphorus would show approximately .050% sulphur and .100% 
phosphorus immediately after the blow. These percentages are affected 
but slightly by the recarburizer. 


■ S'. ^ 

Chemistry of Recarburizing and Deoxidizing: The importance of 
this part of the operation is more fully appreciated when it is recalled that 
the Bessemer process was made a commercial success only through deoxi¬ 
dizing with manganese. This element, then, plays a very vital part, the 
effect in the product most evident being the prevention of that combination, 
of hot and cold shortness commonly spoken of as rottenness. It is due to 
the presence in the metal of iron oxide, FeO, which is dissolved by molten 
iron. This oxide is reduced by metallic manganese, thus: (a) FeO+Mn= 
MnO-j-Fe. As MnO is not soluble in iron to any appreciable extent, reaction 
(a) will result in ridding the steel of all but traces of metallic oxide. Carbon 
may.act as a deoxidizer, according to some authorities, as shown by 
reaction (b). 

(b) FeO+C=Fe+CO. 

However, the evolution of CO gas that produces the violent boiling of the 
metal in the ladle, which boiling often continues also in the ingot mould after 
the metal has been teemed, is probably caused by CO and other gases passing 
out of solution in the metal as the latter cools. Small amounts of these gases 
retained by the steel produce the blow holes previously alluded to. It is 





CHEMISTRY OF THE PROCESS 


197 


to be noted, also, that manganese offsets the evil effects of sulphur as will 
be explained in a later chapter. The silicon as well as the carbon and 
manganese in the ferro or spiegel and pig iron will also serve as a deoxidiz¬ 
ing agent. Besides, silicon, by attacking CO, prevents the formation of 
blow holes. For the greatest effectiveness a considerable excess of silicon 
and manganese over that required by their respective reactions should 
be used. This is one of the reasons why the manganese in steel will range 
from .30 to 1.00%. Additional losses of the manganese in the recarburizer 
are likely to occur by reacting with the silicate of iron oxide, thus: 

(c) FeO *Si0 2 +Mn==MnO *Si0 2 +Fe. 

A study of Bessemer slags shows that a slight decrease of iron oxide without 
a corresponding increase of MnO takes place on recarburizing. This cir¬ 
cumstance is usually explained by assuming that one of the following 
reactions takes place: 

(d) FeO+C=Fe+CO or 

(e) 2Fe0Si0 2 +C0=Fe0 -(Si0 2 ) 2 +C0 2 +Fe. 

As was pointed out under the head of teeming, other deoxidizing agents 
may be added to the ingot as the metal is being teemed. The one most 
commonly employed is aluminum. This element is one of the most powerful 
deoxidizers known. Upon being heated to a sufficiently high temperature 
it will react violently with all the metallic oxides, and also many others. 

(f) 3 Fe0+2Al=Al 2 0 3 +3Fe. 

Various alloys are beginning to be used for this purpose, also. One of 
the best is known as “A. M. S.” metal; it is an alloy of aluminum, man¬ 
ganese and silicon, and is said to be very efficient for this purpose. 




198 


THE OPEN HEARTH PROCESS 


CHAPTER VIII. 

THE BASIC OPEN HEARTH PROCESS. 

SECTION !. 

SOME GENERAL FEATURES OF THE SIEMENS PROCESS. 

Early History of the Process: The ever increasing demand for steel, 
which even the phenomenal success of Bessemer was not able to meet 
entirely, soon led many other inventors into the same field. But the only 
process which was destined to become a rival of the Bessemer was developed 
through the invention of the regenerative principle by that prolific inventor, 
William Siemens. In this connection it may be of interest to note that 
Siemens first developed and employed this principle in the construction of 
steam engines, but while several of these engines were built and put into 
use, they were finally abandoned because of the severe wear on the heating 
chambers caused by the high temperature attainable. But it was shown 
that a great saving of fuel and very high temperatures could be obtained 
by the use of the principle, and at the suggestion of his brother, Frederick, 
Siemens then turned his attention to the application of the principle for 
producing high temperatures in furnaces. The first experimental furnace 
was built in 1858, when it was developed that, with large furnaces especially, 
many difficulties were to be overcome, if the full efficiency which the use 
of the principle promised was to be obtained. After two years or iriore 
of experimentation, Siemens fell upon the plan of gasifying the fuel prior 
to burning it in the furnace, when he found that most of his difficulties 
had been overcome. The first furnace burning gaseous fuel, patented in 
1861, was used for making glass. Here, the great advantages of the furnace 
in economy and regularity of working were fully proven, and it was not 
long until it was adopted in other industries, also. Some of these early 
uses of the furnace were for zinc distillation, for puddling, for reheating 
iron and steel, and for melting crucible steel. Siemens next turned his 
attention to the manufacture of steel in his furnace, and, though many trials 
were made at many different works, he met with only indifferent success. 
Finally, like Bessemer, he found it necessary to erect a steel works of his 
own in which the success of the process could be demonstrated. These 
works were located at Birmingham, England, and were at first employed 
in a remelting process by which steel of the best quality was obtained 
from such scrap as old iron rails, plates, etc. In the meantime, Siemens 
was busy developing an idea of decarbonizing pig iron for making steel by 
means of iron ore, and by the year 1868 he had proved that this process 
could be successfully employed. Siemens next turned his attention to 




PRINCIPLES 


199 


evolving a method whereby steel could be produced directly from the ore, 
thus dispensing with the blast furnace. In this feat he actually succeeded, 
but the cost of production was many times that of producing steel from 
pig iron. Nevertheless, he continued his experiments until his untimely 
death in 1883 put an end to his endeavors. He died firmly believing that 
his direct process would eventually supplant all conversion methods. Sub¬ 
sequent endeavors have shown this idea is wrong, and that his pig and ore 
process is the most practicable and economical. 

Principles of Siemens Pig and Ore Process: Briefly, the method of 
Siemens was as follows: He used a rectangular covered furnace to contain 
the charge of pig iron or pig iron and scrap, and provided most of the heat 
for the chemical reactions by passing burning gas over the top of the 
materials. The gas, with a quantity of air more than sufficient to burn 
it, was introduced through ports at each end of the furnace, alternately 
at one end and the other. The gaseous products of combustion passed out 
of the port, temporarily not used for entrance of gas, into chambers partly 
filled with checker brick, which absorbed some of their sensible heat, and 
from these chambers out through a stack. After a short time, the gas and 
air were shut off at the one end and introduced through the heated checker 
chambers at the opposite end, absorbing some of the heat stored in the 
bricks. These gases then entered the furnace with a high sensible heat 
and gave p, higher temperature in combustion than could be obtained 
without preheating. In about twenty minutes, the course of the gas and 
air was reversed, so that they entered through the port first used; and 
a series of such reversals, occurring every fifteen to twenty minutes, w T as 
continued until the oxidation had reached the desired point. The elements 
in the iron attacked by the oxygen of the air and of the iron ore fed in were 
carbon, silicon and manganese, all three of which could be reduced to as 
low a limit as in the Bessemer process. Thus, as in all the other 
processes for purifying pig iron, the basic principle of Siemens’ process was 
that of oxidation. But in other respects it was unlike any other process. 
True, it resembled the puddling process in both the method and the 
agencies employed, but the high temperature attainable in his furnace 
permitted him to secure in the liquid state a perfectly malleable metal 
which could be cast into ingots and be free of slag. In this respect the 
same result was produced as in the Bessemer process, but by a different 
method and through different agencies, both of which imparted to it many 
advantages over the older pneumatic process. 

Advantages of the Process: These advantages may be briefly 
summed up as follows: 1. By the use of ore as an oxidizing agent and by 
the external application of heat, the temperature of the bath is made 
independent of the purifying reactions, and the elimination of the impurit ies 
can be made to take place gradually, so that both the temperature and 
the composition of the bath are under much better control than in the 




200 


OPEN HEARTH PROCESS 


Bessemer process. 2. For the same reasons, a greater variety of raw 
materials can be used and a greater variety of products can be produced 
by this than by the Bessemer process. 3. A very important advantage 
is due to the increased output of finished steel from the same amoimt of 
pig iron, which means that fewer blast furnaces are required to produce 
a given tonnage of steel. 4. Finally, with the development of the basic 
process, the greatest advantage of the Siemens over the Bessemer was 
revealed through the elimination of phosphorus. Comparing the basic 
open hearth with the Thomas-Gilchrist process it is to be noted that, 
due to the different temperature conditions, phosphorus is eliminated in 
the former before the carbon, whereas it is not oxidized in the latter process 
until after the carbon, in what is known as the after-blow. Hence, while 
the basic Bessemer process requires a pig iron with a phosphorus content 
of 2.00% or more in order to maintain the temperature high enough for 
the after-blow, the basic open hearth permits the use of iron of any phos¬ 
phorus content. In the United States this fact is of the greatest importance, 
since, for reasons already explained, it makes available immense ore deposits 
which could not otherwise be utilized. For this reason the basic open 
hearth process has become the leading method in this country. 

Mechanical Changes and Improvements in Siemens Process: As 

would be expected, many variations of the process, both mechanical and 
metallurgical, have been worked out since Siemens first put his method 
into operation. Along mechanical lines various improvements in the 
design, the size and the arrangement of the parts of the furnace have been 
made. Originally, the furnace had a capacity of only four or five tons, 
but now the size ranges from 40 to 100 tons capacity, and in new plants 
the capacity will seldom be less than 75 tons. But the greatest departure 
from Siemens' original plan was made by the invention of the tilting or 
rolling furnace. These furnaces are of two types, and are known as the 
Campbell and the Wellman furnaces, respectively. In each case the 
furnace is built of brick, which are held firmly in piace by a strong frame¬ 
work of steel, and is mounted upon rollers or rockers, thus permitting it 
to be tilted either forward or backward. In the Wellman type the hearth 
and ports are built solid, so that both move together; and as tilting the 
furnace breaks the connections with the regenerator flues, the furnace can 
be fired only when in an upright position. This fault is overcome in Camp¬ 
bell’s invention, in which the hearth only is movable, and the center of 
rotation is coincident with the center line of the ports. By the use of 
water cooled castings, fairly tight joints are made between the hearth and 
the flues, so that the furnace may be tilted in either direction, forward or 
backward, without turning off the gas and air. 

Metallurgical Improvements: The hearth of Siemens’ furnace was 
of acid brick construction, and the bottom was made up of sand—essentially 
as in the acid process of today. Later on, in order to permit the charging 




IMPROVEMENTS 


201 


of limestone for the removal of phosphorus, the hearth was constructed 
with a lining of magnesite brick, which were covered with a layer of burned 
dolomite or magnesite to replace the sand of the acid furnace. These 
furnaces were, therefore, designated as basic furnaces. The pig and scrap 
process was originated by the Martin Brothers. By substituting scrap 
for the ore in Siemens’ pig and ore process they found it was possible so 
to dilute the charge with steel scrap that little oxidation was necessary. 
Since the time of the Martins, these processes have undergone various 
modifications, chief of which are those known as the Talbot, the Campbell, 
the Bertrand-Thiel, and the Monell processes. By using a basic lined 
tilting furnace in which a large bath of the purified molten metal is always 
retained, Talbot succeeded in hastening the oxidation of the silicon, manga¬ 
nese, phosphorus and carbon to such an extent that the operation is made 
more nearly continuous, and the time between heats or tappings is greatly 
reduced. Campbell’s tilting furnace permits him to apply the pig-and-ore 
process to molten metal, because, by tilting the furnace forward, the frothing 
of the bath, produced by the violent reactions, is prevented from throwing 
the slag through the doors as would be the case in a stationary furnace. 
By a combination process, he also aims to make acid steel from basic pig 
iron. In a basic lined furnace he eliminates the silicon, manganese, phos¬ 
phorus and a little of the carbon, then pours this semi-purified metal into 
an acid furnace, where the remainder of the carbon is worked down as in 
the regular acid process. The Bertrand-Thiel process is applied to pig 
iron with a very high phosphorus content, and makes use of the two-period 
scheme of purification, also. In the first period, the furnace is tapped in 
order to separate the metal from the slag, which contains such a high 
percentage of phosphoric acid, P2O5, that it is valuable as a fertilizer. 
The metal is then poured either back into the same furnace or into another 
basic furnace for the final purification. In developing his process, Monell 
had the same objects in mind as Talbot, namely, the rapid conversion of 
basic iron into steel; but he wished to avoid the reservoir of molten metal, 
and make his process adaptable to the stationary furnace. He accom¬ 
plished his object by first charging limestone and ore into a basic furnace, 
heating these until the batch became pasty, then adding molten pig iron, 
when the silicon, manganese, and phosphorus were rapidly oxidized and, with 
the lime, formed a slag that, as the carbon began to be oxidized, foamed 
up and ran from the furnace through slag notches provided for the purpose. 

The Process for the Pittsburgh District: Most of the pig iron 
available in the Pittsburgh district contains a fairly high percentage of 
phosphorus, and the mills produce considerable scrap. Hence, the furnaces 
are practically all basic—the Carnegie Steel Company no longer operates 
any acid open hearth furnaces—and a combination of the pig-and-ore, pig-and- 
scrap, and Monell processes is employed. It has been briefly described as 
follows: Limestone is charged on a basic bottom, ore is charged on top 
of the stone, and scrap on top of this; if molten pig iron cannot be obtained 





202 


OPEN HEARTH PROCESS 


in sufficient quantity to complete the charge, some cold pig is charged 
with the scrap; and the entire mass is heated in the furnace for about two 
hours, or until the scrap is white hot and slightly fused. Molten pig iron 
is then added, when a lively reaction occurs, in which almost all of the 
silicon, manganese, phosphorus and part of the carbon are oxidized, the 
first three forming compounds that slag with the iron oxide, and join the 
iron and lime silicates that are already melted. About 80% of this slag 
is drawn off by the end of two or three hours more. The ore acts on the 
carbon for three or four hours longer, during which time, and continuing 
afterwards, the limestone is being decomposed by the heat, and its CO 2 
is bubbling up through the bath and exposing part of the metal to the flame, 
thus oxidizing it and completing the purification started by the ore reaction. 
What is known as the lime action, or boil, lasts two or three hours longer; 
and then, if the charge was calculated correctly, the carbon content will 
be somewhat greater than that at which the metal is to be tapped. 
Ordinarily, of course, the carbon is too low or too high, in which cases 
more pig or more ore must be added. In about another hour the carbon 
content will have been reduced to the proper amount for tapping, which is 
usually about .10%. 


SECTION II. 

EQUIPMENT FOR A MODERN BASIC OPEN HEARTH PLANT. 

The Modern Plant: Besides the furnaces themselves, the modern 
open hearth plant requires considerable additional equipment. Thus, there 
must be provided ladles for containing molten metal; moulds for ingots; 
cranes and charging machines for handling materials; boxes for the solid 
materials; dinkeys or electric-engines for hauling the materials; a stripper 
for removing the moulds from the ingots; a great number of small articles, 
like shovels, wheel barrows, rabbles, etc.; and, finally, apparatus for pre¬ 
paring or controlling the fuel supply. In addition the more modern plants 
will be provided with a mixer, a calcining plant, and also spiegel-cupolas, 
if liquid recarburizers are used. A brief description of the more essential 
items enumerated above is given herewith. 

Calcining Plant: At most of the plants there are cupolas for roasting 
dolomite. These furnaces are cylindrical in form, and each one is so placed 
that one base forms the bottom, the other the open top of the furnace. 
In the usual construction the cupola is made up of an outer shell of boiler 
plate, one-half inch thick, and a double refractory lining made of two courses 
of brick, the inner one being of first quality and the outer one next to the 
shell of second quality fire brick. On the floor of the furnace, there is a 
cone shaped casting which deflects the burnt dolomite, in its descent, 
toward the circumference, where it may pass out through openings provided 
for the purpose in the base of the cupola. For fuel, coke is employed, and 
it must be burned by an air blast. This blast is supplied at a pressure 



PLANT EQUIPMENT 


203 


of five to six ounces. A bustle pipe distributes the air and is provided with 
about eight tuyeres, or connections, with the cupola. Built on the charging 
platform and extending about three feet above it, there is a seat upon which 
the charging bucket is deposited by a crane and from which its contents, 
through a bell and hopper arrangement in the bottom of the bucket, may 
be dropped into the cupola. Usually the ratio of materials in the charge is 
two buckets of dolomite to one bucket of coke. Thus, the fuel consumption 
is about 15% of the weight of dolomite calcined. The operation of burning, 
in which the CO 2 is expelled from the stone, leaving calcium and magnesium 
oxides (CaO and MgO) in place of their carbonates (CaC 03 and MgC 03 ), 
requires from ten to twelve hours. The burning period is controlled by the 
rate at which this material is withdrawn. As fast as the dolomite is 
burned it is shoveled out at the bottom, crushed to pass a half-inch mesh, 
then conveyed to the loading bins, whence it is later taken as required 
to the open hearth. 

Fuels: For fuels in open hearths, natural gas, coke oven gas, producer 
gas, powdered coal, fuel oil and, sometimes, tar are used. The choice of 
fuel depends largely upon the location of the plant. Natural gas is, of 
course, preferable when it can be obtained, as it is of uniform composition, 
is easily controlled and imparts no sulphur to the bath, while coke oven gas, 
producer gas and powered coal are of varying composition and quality and may 
impart some sulphur to the bath. The great demand for petroleum pro¬ 
ducts has made fuel oil too costly, while the supply of tar is so limited that 
it is not always available as an open hearth fuel. There remains, then, as 
the principle substitutes for natural gas, only powdered coal, coke oven gas 
and producer gas, all of which have already been discussed in the chapter on 
fuels. (See Chapter IV., Section 6). In either case, coal of the best grade 
obtainable is desired, especially with respect to sulphur, as there is always 
danger of its being absorbed by the bath. In using coke oven gas frcm 
which the benzol has been removed, it is found necessary to bum with it some 
substance like tar, for example, that will impart luminosity to the flame, as 
otherwise the poor visibility within the furnace makes it difficult for the 
melter to control the temperature. In the new plants of the Carnegie Steel 
Company, the producers are connected in sets of four—five in one or two 
cases—• and each set serves two furnaces, the gas mains from the producers 
being arranged so that any one or all of the producers in a set may discharge 
into either one or both of the furnaces. 

Fuel Consumption: It is a difficult matter to arrive at any conclusion 
as to the amount of heat required to produce a ton of steel. It is subject to 
a number of conditions such as kind of fuel used, condition of the furnace 
and checkers, continuity and rate of production, and the care and intelligence 
with which the furnace is operated. In actual practice the number of heat 
units per ton of steel produced is found to vary from 5,000,000 B. t. u. to 6,000,000 
B. t. u. when natural gas is used, and from 6,000,000 B.t.u. to 8,500,000 B.t.u. 
when other fuels are employed. An inspection of the fuel records of several 




204 


OPEN HEARTH PROCESS 


different plants and a consideration of averages for long periods of time, vary¬ 
ing from six months to a year, indicate that the fuel consumption per gross 
ton of steel produced, to be considered good practice, should be about as follows: 
natural gas, 5,000 cubic feet; coke oven gas, 8,0G0 cubic feet, with 16 gallons of tar; 
tar alone, 45 gallons; producer gas equivalent to 600 pounds of coal; and 
powdered coal, 500 pounds. 

Hot Metal Mixer: The advantages of the hot metal mixer have 
already been discussed in connection with the Bessemer process; and 
although the conditions in the open hearth plant, where large quantities 
of metal are needed at irregular and uncertain intervals of time, are exactly 
the reverse of those in a Bessemer plant, which requires small quantities 
of metal at short and comparatively regular intervals, these advantages 
are as applicable to the one case as to the other. In order that these 
advantages may be realized to the fullest, open hearth mixers should have 
a large capacity. One large mixer of 1000 or 1200 tons capacity is to be 
preferred to two of 500 tons capacity. 

Spiegel Cupolas: In plants manufacturing large quantities of medium 
high carbon, high manganese steels, such as is used for railroad rails, for 
example, the use of spiegel for recarburizing may be advantageous, in which 
case cupolas for melting the spiegel mixtures are an important adjunct 
to the open hearth plant. In construction and operation, these cupolas 
are similar to those already described for the Bessemer plant. For collect¬ 
ing and weighing the different ingredients of the charge, a larry car equipped 
with a multiple beam scale is most convenient. In charging, the metallic 
parts of the burden, consisting usually of spiegel and pig iron, are 
charged into the cupola together, while the coke, with which is mixed 
enough limestone to flux its ash, is charged separately. The proportion 
of coke required in each round will vary somewhat, but in good practice it 
will seldom exceed seven per cent, of the weight of the metallic part of the 
charge. To secure greater uniformity and provide an ever-ready supply of 
molten recarburizer, the cupolas attached to the most modern plants are 
provided with a small mixer. By means of brick and clay lined runners the 
metal from the tap hole of each cupola is conducted directly into this mixer, 
from which definite amounts may be taken as desired. For weighing the 
recarburizing metal, a track scale, on which the transfer ladle may rest 
during the pouring, is placed on the track directly in front of the mixer. 
The manganese content of the molten recarburizer is varied to suit the 
requirements of the different grades of steel by varying the amount of 
pig iron with which the standard spiegel is diluted. Varying the proportion 
of pig iron to spiegel also changes the carbon content of the mixture slightly. 
With a given weight of standard spiegel, the more pig iron charged the lower 
the carbon content of the mixture will be, as can readily be seen by 
comparing the analyses of these materials. 

The Steel Ladles: The ladle for receiving the steel is made of boiler 
plate and is lined with two courses of brick each 234> inches thick. The first 
layer, next to the shell, is usually of fire brick, while the second layer is of 




PLANT EQUIPMENT 


205 


white river brick. Both courses are laid on end in a mortar of fire clay, to 
which a little loam is sometimes added. The capacity of the vessel is depen¬ 
dent on the amount of steel to be handled in each heat, which in turn is fixed 
by the capacity of the open hearth. The opening at the bottom of the ladle 
is provided with a fireclay nozzle about two inches in diameter, which may 
be closed by a stopper. The stopper is made of clay bonded graphite and 
is mounted on a rod, protected by fireclay sleeve brick, that reaches to the 
top of the ladle; there it is connected to a sliding bar on the outside that can 
be raised or lowered by a lever near the base. Both the stopper and the 
nozzle must be replaced after each heat. Great care is necessary both in 
placing the nozzle and in setting the stopper in the nozzle, for a bad fit 
results in a running stopper, which may cause a great waste of metal. To 
prevent the steel from chilling about the stopper, powdered coal is often 
thrown into the depression around the nozzle just before tapping a heat. 

The Stripper: The action of this machine has already been described 
in connection with the Bessemer process. The ingots must all be sufficiently 
cooled before stripping, so that there will be no danger of breaking the 
solidified wall of metal. After being stripped, the ingots are then ready to be 
sent to the soaking pits previous to the rolling. To strip an ingot, it is only 
necessary, in the majority of cases, to place the jaws of the stripping machine 
under the lugs on the mould and apply the lifting force, when the mould 
will slip from the ingot and can then be raised to a sufficient height to 
transfer. It is only at times, usually due to a defective mould or to 
metal being splashed over the top edges from a running stopper, that the 
moulds are not slipped off easily, and then the plunger is rested on top of 
the ingot as the mould is drawn upward. When this treatment fails to 
loosen an ingot, it is sent to the mould yard where more time is available 
for extracting it and where it may be subjected to various treatments 
according to the means at hand and the cause of its sticking. 

Moulds: Alter the ingots of each heat are stripped the empty moulds 
are stored in the mould yard imtil they are sufficiently cool to be drawn back 
to the open hearth for another charge, and during the wait they are 
inspected and cleaned of adhering particles of steel that may remain 
about the top from splattering in pouring. Any damaged moulds 
that cannot be used are charged as cold iron, as they are cast 
from a good grade of Bessemer pig iron. Many types and sizes of 
moulds are used. Heavy moulds chill the surface of the steel quickly 
and hasten the solidification, which always proceeds from the wall of the 
mould toward the middle of the ingot. Since steel contracts on solidifying, 
there is a cavity left directly under the top surface of the ingot, as the 
metal in this location is the last to solidify. This cavity, called the pipe, 
is responsible for the production of a great deal of scrap in rolling the steel. 
There are numerous methods to reduce the size of the pipe and to keep it 
as near the top as possible, but it cannot be entirely eliminated. The 
principle of most of the devices is to keep t^ie top of the ingot molten longei 



206 


OPEN HEARTH PROCESS 


than the bottom, so that the molten steel on top will flow into the cavity 
as fast as it forms and thus lessen the extent of the pipe. The Gathman type 
of mould depends upon uneven thickness of mould wall to effect the same 
result. By having the mould thin at the top and thick at the bottom, 
the thin top has a less chilling effect on the molten steel at the top, 
which, therefore, is the last to solidify. A similar method consists in 
lining a removable top of the mould with brick or clay, thus preventing 
rapid conduction and radiation. Some try to keep the steel at the top of the 
ingot fluid by a coke, a charcoal or a gas fire. Many other more complicated 
devices have been invented, also, but their use involves much additional 
expense. Besides, piping is regarded by many as a necessary evil, and the 
safest way to avoid it is to allow a proper discard from the top of the ingot, 
which discard is cut off at the blooming mill shears. Armor plate ingots 
are sometimes cast in specially constructed hard sand moulds. Ingots 
for this material are always bottom cast, two ladles being poured at the 
same time, which are followed frequently by a third, pouring directly into 
the mould. There are standard sinkheads for all armor plate ingots. 

The Charging Machine: Of all the labor saving devices employed 
about the open hearth plant, none have brought a greater saving of money 
and time than the charging machine. Indeed, it may be looked upon as the 
most essential part of the equipment, for if the charging were done by hand, 
the time thus lost, especially in the case of the large furnaces, "would be 
so great that this feature would appear as a serious drawback to the process. 
There are several types of these machines, but the ones most generally 
employed are of the iow ground type. They consist of two main parts. 
First, there is the bottom truck made up of a very strong steel frame-work 
and mounted on flanged wheels which travel on a very wide gage track 
laid in front of the furnace. Next, there is the charging carriage, which 
moves over a track, laid on the frame of the truck, at right angles to the 
direction of motion of the truck itself. On this carriage is mounted a 
kind of lever, the long arm of which extends toward the furnace and is 
known as the charging bar. The charging bar is hollow to provide space 
and bearings for the locking bar, about which it can be made to revolve, 
and is shaped on the end to fit into the socket of the charging box. The 
charging bar is thus capable of giving eight different primary motions, 
or any number of resultants of these motions. In operating the machine, 
the charging boxes rest on buggies running on a narrow gage track between 
the machine and the furnace. First, the truck of the machine is moved 
so that the charging bar is directly opposite the charging box to be emptied, 
then the carriage is moved forward to bring into position the end of the 
charging bar, which is then dropped into the socket on the end of the 
charging box and locked in position by advancing the locking bar until its 
front end projects into a hole provided for the purpose in the socket of the 
box. Now, the machine is made to serve for a shifting engine, and, by 
moving the truck, the whole train of charging boxes may be moved along 
in front of the furnace, so that tfie box engaged is brought directly opposite 




PLANT EQUIPMENT 


207 


the door. The charging bar is then raised, carrying the box with it, and 
by a forward motion of the carriage the box is passed into the furnace, 
where, by rotating the charging bar, the box is turned upside down and 
its contents deposited. By reversing these motions the box is then placed 
upon the buggy again. The charger will pick up and empty a box in less 
than a minute. As the capacity of the box is more than one ton, for even 
the lightest materials of the charge, it is possible to charge even the very 
large furnaces in less than an hour. Charging machines are always elec¬ 
trically operated. 

Charging Boxes: The charging boxes are made of cast steel or of five- 
eighth inch boiler plate with cast steel ends. One end of the box is provided 
with a socket opening from the top so that the T section on the end of the 
charging machine peel, or arm, may readily be inserted and withdrawn from it. 
The boxes have a capacity of sixteen cubic feet or more, and into them all 
solid material for the furnace charge is placed. For transporting the boxes 
from place to place about the works, buggies are provided. These buggies 
are of standard or narrow gage type, are made of cast iron and accom¬ 
modate three to four boxes each. 

Stock Yard: There is usually one stock yard to each plant. In it are 
kept the stores of limestone, ore, cold pig and, sometimes, scrap, from 
which materials the cold charges for the furnaces are made up. The ore 
and limestone are loaded into the boxes from chutes or by grab buckets, 
depending upon the manner of storing; the cold pig from railroad cars or 
from a stock pile by means of a magnet; while the scrap is brought from 
the rolling mills ready loaded in the charging boxes, or if it is delivered 
in railroad cars, it is transferred to them by magnets. Soft ore is 
generally used to make up a charge on account of its lower cost, because 
there is no advantage in charging lump ore on the bottom, and it is not 
necessary to have as pure an ore as is the lump ore. After a charge is 
made up, the buggies are pushed over platform scales and weighed by 
the weighmaster, who records the weights in a stock book. The stock- 
yard men take into account the amount of pig iron to be used and, to a 
certain extent, the carbon contents of the scrap charged and add to the 
charge what ore they think will be necessary. Reports giving the 
weights of all materials are made out in triplicate, one of which is sent 
to the melter, so that after it reaches the furnace front the melter-foreman 
or his first helper may vary the ore charge to suit their plans or ideas. 

Arrangement of the Plant: The furnaces of the plant are always 
enclosed and covered by an immense steel building, and in the modern 
plant the furnaces are arranged end to end in a long row along the center 
of this building. That part of the floor of the building along the front, 
or charging side, of the furnace is called the charging floor. On this floor 
and next to the furnaces is laid a narrow gage track on which the solid 
materials are conveyed to the furnace for charging, while, back of the narrow 
gage track, there extends a very wide gage track, with a spread of about 





208 


OPEN HEARTH PROCESS 



Fig. 25. Model of 100-Ton Producer Gas Fired Open Hearth Furnace. View from Tapping Side. 













THE OPEN HEARTH FURNACE 


209 


twenty feet, for the charging machines. The space above this floor and 
the furnaces is spanned by two or more electric overhead cranes. The 
remaining floor space of the building lying along the tapping side of the 
furnace is called the pouring floor, and is also spanned by electric cranes. 
These two floors may be on the same level, as in some of the older plants; 
but all the new plants are of the two=level type, that is, the pouring floor 
lies some twelve to eighteen feet below the level of the charging floor. 
The pouring platforms, six to eight feet wide and about eight feet high, 
are located along the outer edge of the pouring floor. The mixer and 
cupolas are often located at one end of the open hearth building, as this 
arrangement permits the transfer of the hot metal to be made with the 
cranes. However, in large plants this arrangement would be inconvenient, 
as it would interfere with the work of the cranes, so the hot metal is carried 
to the different furnaces on a track laid on the charging floor. With this 
arrangement the mixer may be located at any convenient point. When 
producer gas is used for fuel, the producer plant is built back of the open 
hearth plant, parallel to the charging floor. The calcining plant, stock 
yard, and mould yard are located at points as convenient to the open 
hearth house as possible. The stripper should be placed so that the steel 
is always advancing toward the soaking pits of the blooming mill, though 
this matter is but a question of convenience. 

SECTION III. 

CHIEF FEATURES OF BASIC OPEN HEARTH CONSTRUCTION. 

Parts of the Open Hearth Furnace and Their Arrangement: An 

open hearth furnace consists of the furnace proper, containing the covered 
laboratory, hearth or bath, in which the charge is placed; ports for admitting 
the gas and air over the charge; regenerative chambers, containing checker 
brick for storing up heat from the products of combustion and imparting 
it to the cold gas and air; flues and uptakes, connecting the checker chambers 
with the furnace proper; slag pockets, which are located at the base of the 
uptakes; flues, leading from the air and gas supply (if producer gas is used) 
to the checker chambers, with connections to the stack; valves for regulating 
the direction of flow of gas, air and waste gases; and the stack itself. The 
furnace proper is located on the level of the charging floor and rests on 
a concrete foundation. The slag pockets, checker chambers, flues and 
valves are all located in a cellar, on a level about fifteen feet below the 
charging floor in houses of the one level type, or on the first floor level in 
the two level type. The checker chambers are not located under the furnace 
proper but under the charging floor in front of it, and the stack is placed 
a short distance beyond nearer the gas producers. The base of the stack 
flue sets on a level with the bottom of the checker chambers, but the 
stack proper begins at the charging floor level. 

The Furnace Proper: The furnace, itself, is a rectangular brick 
structure, supported on the sides and ends by vertical steel buck-stays in 
the form of channels or slabs, four to five and one half inches thick and 




210 


OPEN HEARTH PROCESS 


eleven inches wide, and bound together at their tops, both longitudinally 
and crosswise, by stays and tie rods. The most recently constructed 
furnaces have a capacity rated at 100 tons. Such a furnace is 
approximately eighty feet in length and twenty feet in width, outside dimen¬ 
sions over all. Ten sets of buck-stays on the front and rear sides, and 
four or six sets on the ends are required to furnish the requisite support 
against expansion of the brick work. The buck-stays are held in place by 
12-inch channels placed at their tops. These channels extend entirely 
around the furnace, those along the sides being securely tied with bolts 
and clamps to those crossing the ends of the furnace. The front and 
rear buck-stays are united by tie-rods which are two and one-half inch 
steel rounds; the ends of these extend through the buck-stays and are 
threaded to receive nuts to hold them in place so that they can be tightened 
and loosened according to the expansion and contraction of the furnace. 
The foundation imder the furnace proper is built of concrete, and is of 
such depth and shape as to bear the superimposed load with reasonable 
safety. It is usually in the form of two large piers, with an arched 
opening separating them. The furnace proper comprises the hearth, the 
side walls, and the roof. 

The Hearth is constructed as follows: On top of the concrete foun¬ 
dation is placed a layer of three feet or more of second quality fire brick, 
and upon these is laid a two foot layer of first quality fire brick in which 
a number of 15 inch I-beams are placed to act as a bottom anchorage for 
the vertical buck-stays which surround the furnace; a nine inch layer of 
magnesite brick is then laid on top of the firebrick, and upon these bricks, 
a bottom is made up approximately ten and one-half inches thick with a 
mixture of burned magnesite, 75%, and ground basic slag, 25%, which is 
sintered into place. Dolomite may be substituted for the magnesite, but 
in this case the bottom must be much thicker than when magnesite is 
used. When complete, the hearth has the form of a shallow dish whose 
sides extend up to the level of the charging doors. In order to obtain this 
shape the succeeding courses of magnesite brick are stepped back, until 
the normal thickness of side wall, about thirteen and one-half inches, is 
reached. The exact hearth dimensions, inside, between fifteen and sixteen 
feet in width and about forty feet in length, are dependent upon the desired 
maximum capacity of the furnace and incidental features. The depth is 
such that the bath of molten metal will be from twenty to twenty-four 
inches deep. The back wall of the hearth is pierced at its exact center for 
the tapping hole, which is about eight inches in diameter and is provided 
on the outside with a removable cast iron lip for receiving the end of the steel 
spout, the function of which is to conduct the molten steel from the furnace 
to the steel ladle at the time of tapping. The slag hole is placed about 
fifteen feet from the tap hole and near the upper edge of the hearth. It is 
surrounded with magnesite brick and is provided with an iron casting at 
its base for the attachment of the cinder spout. 

The Walls are begun on the top course of magnesite brick that sur- 




CONSTRUCTION OF FURNACE 


211 


rounds the upper edge, or brim, of the hearth. They are built of silica 
brick, are about thirteen and one-half inches thick and extend to a distance 
of about eight feet above the charging floor level. The back wall is built 
up solid except for the tapping hole and slag hole, but the front wall 
contains the arched doorways for charging. The doors are usually five 
in number, the middle one being in the middle of the furnace, and are so 
placed that their bases, or sills, are a few inches above the slag line. 
Each opening is provided usually with a water cooled cast steel frame, 
placed between two buck-stays to which it is fastened, and is closed by a 
water cooled, fire brick lined cast iron or steel door that may be lifted 
vertically either by hydraulic or electric power. A wicket, or peep hole, 
is placed on the center line near the bottom of each door. 

The Roof over the hearth is made of silica brick, about twelve inches 
thick, and is arched from front to back only in the newer furnaces, but 
sometimes, also from end to end in older types. The roof is built inde¬ 
pendent of the walls, and rests on skew back brick set in water cooled 
skew back channels that are riveted or bolted to the buck-stays of the 
furnace. 

The Bulk Heads which form the ends of the hearth below the ports 
were originally built of solid brick work and were a source of much trouble, 
as they burned out rapidly. These difficulties were all avoided by replac¬ 
ing much of this brick work with a large, hollow cast steel box with open 
ends to provide for air cooling. The inside surfaces of the bulk heads 
are made of magnesite brick. 

The Ports: The air and gas ports at each end of the furnace are built 
at an angle to the bath, so that the flame is directed against the bath and 
away from the roof. In order to protect the roof and promote the mixing 
of the gas and air, the air enters above the gas. The bricks separating 
the two ports are protected by a water cooling system. Where natural 
gas is used, unless the furnace was constructed for producer gas, there is 
but one port at each end of the furnace, the gas entering on each side of 
either end of the furnace behind a bridge wall, which extends across the 
furnace in front of the well, or up-take, from the checkers. This wall is 
usually made of magnesite brick, though chrome brick is well suited for 
the purpose, and is about thirteen and one-half inches thick and nine inches 
high. 

The Up-and-Down-Takes are the vertical flues which connect the 
air and gas ports with the slag pockets *and the fan-like flues leading to 
their respective checker chambers. They are built of silica brick and are 
not water cooled. In producer gas fired furnaces there is a pair of up-and- 
down-takes for air at each end of the furnace, the two in each pair being 
at opposite sides of the furnace. The up-and-down-takes for the gas rise 
with their centers coincident with the center line of the furnace and may 
stand out with three walls exposed, designated as the dog=box type, or 
be built in between the air flues. For a 100-ton producer gas fired furnace 
these flues are each four feet by three feet, inside dimensions. 



212 


OPEN HEARTH PROCESS 


Arrangement of Up=and-Down=Takes for Natural Gas, Coke Oven 
Gas, Powdered Coal and Tar: The construction of the up-and-down- 
takes in a natural gas fired furnace is much simpler, as it is only necessary 
to have one up-take for the air at each end of the furnace. This up-take 
in modern furnaces is circular, with a diameter of about six and one half 
feet, and is therefore called the well. The air, as it rises, is deflected 
downward toward the bath by the port, which is arched from front to 
back but is straight, longitudinally, with a downward slope toward the 
hearth. This roof is usually about nine inches thick, except near the 
neck where it joins the roof of the furnace. Here it increases to twelve 
inches on account of this point being subjected to the greatest wear. 
The bridge wall previously described, which crosses the port adjacent 
to the up-take, causes the incoming air to roll down past the opening from 
the gas pipes, one of which enters at each side of the port. Thus, there are in 
all four pipes to a furnace. These gas pipes have a diameter of four inches. 
The main supply pipe usually passes over an entire row of furnaces. 
A branch line, provided with a meter, a valve, and a three way cock, leads 
to each furnace, where it again branches into the four inch pipes which 
enter the ports. For tar and powdered coal the same construction as for 
natural gas has been employed, because, so far, these substances have been 
used only as a substitute for the latter fuel when the supply became low. 
Both these substitutes are introduced into the furnace by inserting the 
nozzles of the burners through small openings in the brick work closing 
the ends of the furnace, one burner at each end of the furnace being required. 

Slag Pockets: The slag pockets are chambers at the bottom of the 
up-and-down-take flues. Their functions are to serve as flues to conduct 
the gases to and from the checkers and to catch any solid matter carried 
over with the products of combustion, thereby preventing most of this 
slag material from reaching the checkers and clogging them up. The 
pockets are designed large enough so that only in extreme cases do they 
have to be cleaned out more than once every run. In the 100-ton producer 
gas fired furnace, they are about three feet six inches wide, and eight feet 
high. The two at each end of the furnace are separated by a three foot 
silica brick wall. The outside walls are two feet seven and one half inches 
thick for the air, and three feet for the gas side; the former have ail inside 
lining of silica brick, set against first quality fire-brick, while the latter is 
made of silica brick only. The floor and roof are covered inside with 
silica brick, the latter being arched on a radius of half the width of the 
pockets. One end of each pocket merges into a short, fan-like flue, called 
a neck, which leads to the top of its regenerator chamber. 

Regenerators for Producer Gas: The regenerators, of which there 
are two pairs to a furnace, are built out in front of the furnace and under 
the charging floor, about half below and half above the casting floor 
level. They are separated from the furnace by a distance of about 
four feet. Each pair is made up of one checker chamber for gas and one for 





CONSTRUCTION OF FURNACE 


213 




























































































































































214 


THE OPEN HEARTH PROCESS 



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Fig. 26. Longitudinal Vertical Section of 100-Ton Open Hearth Furnace, 


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CONSTRUCTION OF FURNACE 


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215 



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Showing Slag Pockets, Flues, Ports and Hearth. 


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216 


OPEN HEARTH PROCESS 


air, arranged so that the outer wall of the gas chamber is nearly in line 
with the end of the furnace. The gas chamber is always smaller than the air 
chamber, because the larger volume of air is necessary to burn the gas and 
assist in the oxidation of the bath. The total space actually occupied 
by the checkers in all four chambers is from 120 to 150 cubic feet per ton of 
furnace capacity. For a 100-ton furnace the volume of the checkers in 
the air chamber is between 3500 and 3600 cubic feet while the corresponding 
volume in the gas chamber is between 2500 and 2600 cubic feet. 

The gas chambers on such a furnace, measured inside, are about 
thirty-one feet long, eight feet wide and sixteen and one half feet high from 
the bottom to the base of the roof, which is arched to rise twenty-three 
to twenty-five inches higher. The air chambers are of the same length 
and height, but are about eleven and one half feet wide, and the arch 
in the roof rises about thirty-four inches. The walls of both gas and air 
chambers are built usually with nine or thirteen and one half inches of 
common brick on the outside and thirteen and one half inches of first 
quality fire brick on the inside, and are reinforced on the two sides and 
the free ends by channel buck stays and tie rods. At some plants the 
two chambers in a pair are built en bloc with a single dividing wall 
between them. In this plan of construction the dividing wall is about three 
feet thick and is built entirely of first quality fire brick. The floors of the 
chambers are started usually with a nine inch layer of concrete, which is fol¬ 
lowed with a heavy coat of tar as a water proofing. On the tar is laid 
another nine inch layer of concrete, then four and one half inches of common 
brick and four and one half inches of first quality fire brick. On this floor, 
are laid nine inch fire brick withe walls, which divide the gas and air 
chambers longitudinally into three and four flues, respectively, to a height 
of about four feet. These walls are spanned by fire brick tile, size, 
3"xl2"x31", and on these tile, the checker work, of best quality fire brick, 
size, 43^"x4b^"xl0^ ,/ , is begun and continued to within about three and 
one half feet of the top of the gas chamber, or to within about four feet 
of the top in the air chambers. The arched roofs of the regenerators 
are of fire brick and thirteen and one half inches thick. The checker 
work is separated from the flues leading to the slag pockets by a solid 
wall which rises to their top. This wall aids much in preventing slag 
and dust from being carried into the checkers. But in spite of all 
precautions, some dirt is carried over into the chambers, which causes 
them to become choked eventually, when the furnace must be closed down 
until the checkers are cleaned or replaced. 

Regenerators for Natural and Coke Oven Gases: At some plants 
where natural gas or coke oven gas is used, as for example at Homestead 
and Clairton where natural gas was originally the only fuel employed, the 
gas chamber, in addition to the regular air chamber, is utilized to preheat 
the air. The original idea was to construct the regenerative chambers so 
that in case gas producers were built, the change in fuels would not necessi- 





CONSTRUCTION OF FURNACE 


217 


tate a rebuilding of the furnace; but, now, the chambers for natural gas 
are all being constructed in this manner, because it was found that when 
two air checkers at each end of the furnace are employed, better results 
are obtained than when only one is used. Where one large checker is 
operated, the air and stack gases, instead of flowing to all parts of the 
chamber, tend to take a direct course through the center, thus markedly 
decreasing the efficiency of the chamber. 

Regenerators for Powdered Coal: The use of powdered coal for fuel 
introduces a serious difficulty in the operation of the regenerators because 
of the large percentage of ash that is carried over into the chambers by 
the draught. This fume soon clogs the ordinary checkers to such an extent 
that they are no longer efficient. Two different types of regenerators, 
namely, the arched and columnar types, designed with the idea that they 
would permit the ash to be cleaned out of the chamber without tearing 
out the brick work, have been tried; but as the ash fuses upon the bricks, 
these schemes are impracticable and have consequently been abandoned 
in favor of the old style of construction. But instead of the usual checker 
brick a large tile, measuring about 24"x9"x4", has been substituted, which 
gives larger openings for the passage of the gases. This construction 
appears to be much more satisfactory than either of the others that have 
been mentioned. 

Flues and Valves: While the openings into the slag pockets are at 
the top of the checker work, the openings for the ingress and egress of 
gases at the opposite end of the checker chamber are at the bottom. Here 
the small flues formed by the withe walls open into a large one which leads 
to the stack flue in the case of the air chambers, or, in the case of the gas 
chambers,to a three-way water sealed valve,one of the best types of which is 
represented by the Ahlen valve. Another branch of this valve leads to 
the stack and the third to the gas main. These valves, together with the 
dampers and mushroom valves in the flues from the air chambers, supply 
the means by which the reversals of the flame are made. In the modern 
furnaces, these valves and dampers are connected so that the reversal of 
the air and gas currents take place simultaneously. All the valves and 
dampers are controlled from the charging floor. Since natural gas, and 
also coke oven gas, cannot be preheated without decomposing them, the 
valve system in furnaces using these fuels, as well as those using powdered 
coal, is much simpler than for those using producer gas. 

The Stack: The stack for each furnace must be of such size and height 
as to supply sufficient draught to the furnace. It is lined with first quality 
fire brick, and usually has an inside diameter of 5 feet and a height of from 
140 to 160 feet above the charging floor. The shell is made of % inch boiler 
plate. It usually rests on a concrete foundation, on the same level as the 
floor of the checker chambers, and at this level it has openings for flues 
from the gas and air chambers, as previously described. For controlling the 
draft a damper is placed in the main flue at its entrance to the stack. With new 
or clean checkers this damper partly closes the main flue, but as the checker 
becomes clogged, it is raised from time to time as required. 




218 


OPEN HEARTH PROCESS 


SECTION IV. 

OPERATION OF A BASIC OPEN HEARTH—PURIFYING THE METAL. 

Furnace Attendants and Their Duties: For the work on each 
furnace, three men, a first helper, a second helper and a cinder-pit-man, are 
needed, and besides these, there is a foreman, called a melter foreman, in 
charge of a number of furnaces. Ordinarily, the first helper has charge of the 
furnace except at the tapping of a heat. He informs the charging machine 
operator of the amount of ore the charge will require and how and where 
to place the various parts of the charge; he regulates the heating of the 
furnace; runs off the slag; directs any repairs necessary during the operation; 
and has charge of working the heat, that is, making the necessary additions 
of ore, pig, spar, etc. to prepare the steel for tapping. But when the heat 
is ready to tap, the melter foreman takes charge. The first helper, subject 
to the supervision of the melter, actually taps the heat, and, after doing 
so, he directs the repair of the bottom and helps make up the banks and 
clean up the steel spout. The second helper is next in charge; he keeps 
a supply of dolomite, feed ore, fluorspar, ferro-manganese and ferro-phos- 
phorus on hand and places the solid recarburizing additions on the platform 
convenient to the ladle. He helps to work the heat, digs the plug out of 
the tapping hole when the heat is ready to tap, keeps the tapping hole 
open and clean while the furnace is being rabbled, and assists in making 
up the banks of the furnace preparatory to recharging. He also attends 
to the plugging of the tapping hole, relines the steel spout after each heat 
and cleans up aroimd the furnace. The cinder-pit-man attends to the 
cleaning of the pits, from which the slag and metal must be removed after 
each heat. In addition, he assists in making bottom at his own furnace 
and all the others under his melting foreman. The melter, or foreman, 
usually has charge of a group of six or seven furnaces. He takes charge of 
any furnace in his group when any serious difficulty arises, and he always 
has charge of the tapping of the heat. He receives an order for the kind of 
steel desired from the steel distributor, so when the tapping time of a heat 
is near, he orders the recarburizer and moulds necessary, and takes charge 
of the furnace when the carbon is but a few points above the tapping point. 
He decides when the heat is ready, gives the order to tap, and directs the 
addition of the recarburizers. He gives the order for lifting the ladle when 
the steel is out of the furnace, superintends the teeming of the steel, and 
inspects the bottom of the furnace after the heat is out. 

Preparation of the Furnace for Its First Charge: Starting a new 
furnace is an operation that requires a great deal of care in order to avoid 
injuring the brick work and to prevent explosions, especially when producer 
gas is used for fuel. The complete preparation of the furnace may be said 
to take place in four stages, known as drying, heating, making bottom 
and washing. The drying is begun very slowly with wood or gas fires, 
and requires about twenty-four hours, during which time all the con¬ 
nections to the stack on both ends of the furnace are left open. The 




CHARGING RAW MATERIALS 


219 


temperature is then gradually increased for about another twenty hours. 
When the furnace has almost reached a red heat inside, the products of 
combustion are led off through only one set of checkers for three or four 
hours, then gas is turned on carefully and the real heating is begun, 
which requires about twenty-four hours more. During this time, the 
flame is reversed at intervals of about an hour at first, then more often, 
in order to heat up both sets of checkers evenly and uniformly. When a 
slag-melting temperature has been reached, finely ground magnesite is 
thrown into the furnace to cover the joints between the magnesite brick, 
and a little finely ground basic cinder is scattered on top of it. About 
twelve hours is required for these additions to fuse and make the bottom 
solid. The making of the bottom is then begun. For this purpose burned 
magnesite is much preferred, but as this substance is sometimes very 
expensive, calcined dolomite is employed as a substitute. With the 
former, the procedure is about as follows:—A mixture of burned magn¬ 
esite, 75%, and basic cinder, 25%, both ground to pass a half inch screen, 
is scattered over the bottom and sides of the hearth to a depth of about 
a half inch, and allowed to sinter. At the end of about three hours, the 
gas is turned off, and another layer of the mixture is thrown in; and this 
procedure is repeated, at the same intervals of time, until the bottom 
and banks have been built up to the desired thickness of about eleven 
inches, which occupies about ten days in all. The tapping hole is next cut 
through from the outside, to terminate on the bottom, and is then filled 
up with burned dolomite, held in place by a cap of clay on the outside. 
The furnace is then ready for the wash heat. About twenty tons of basic 
cinder is charged and melted. This melt is rabbled up against the banks 
so that every part of the hearth is made solid, and is then tapped out. 
Burned dolomite is now piled on top of the banks as high as possible, 
when the furnace is ready to receive its first charge. 


Charging: The first charge consists of limestone, scrap, and cold pig 
iron; neither ore nor hot metal are used on a new bottom until it shows 
it is not absorbing iron and is absolutely solid. Trade heats, of approxi¬ 
mately half scrap and half hot metal arechargedfor the first half dozen heats, 
after which the percentage of hot metal is increased as rapidly as possible to 
the normal. The materials in the charges vary for different kinds of heats, 
but in general, a so-called Monell heat requires from 75% to 100% hot metal 
and a trade heat less than 75% hot metal. In each case, the remainder of the 
metallic part of the charge consists of scrap, while the ore and limestone are 
varied to suit the conditions. An example of each as used on a 100-ton funrace 
follows: 


Monell. 

Limestone.... 20000 pounds. 


Ore. 40000 pounds. 

Scrap. 45000 pounds. 

Pig Iron.165000 pounds. 


Trade. 

Limestone. ... 17000 pounds. 


Ore. 10000 pounds. 

Scrap. 95000 pounds. 

Pig Iron.115000 pounds. 










220 


OPEN HEARTH PROCESS 


In place of ore, briquettes, made from blast furnace flue dust, or heating 
furnace cinder may be substituted. The charge, with the exception of the 
molten iron, is brought to the furnace in the charging boxes previously 
mentioned, and charged by machine. Hot metal is brought, either from 
the mixer or from the blast furnace direct, in ladles and is then poured 
into the furnace through a runner that is introduced at one of the doors 
for the purpose. Other additions in small quantities are thrown in by 
hand through the doors. At one plant, furnaces with removable tops are 
provided, in order to make it possible to charge very large pieces of scrap 
which would not pass through ordinary doors. At all plants advantage is 
taken during repairs to old furnaces to charge such large scrap through 
the top before the roof is put on. As to the grade of the materials in the 
charge, it is preferable to have an iron low in sulphur and silicon because 
the former element is only partly removed in the furnace, if at all, and the lat¬ 
ter, upon being oxidized to silica, rapidly cuts away the banks. A manganese 
content between 1% and 2% is also desirable, as it assists somewhat in the 
removal of the sulphur. As there is almost a complete elimination of 
phosphorus in the process, the quantity of this element in the charge is 
not of great importance up to one per cent. As previously indicated, 
the pig iron, in order to save time and conserve heat, is charged in the 
molten state whenever possible. 

The Order of Charging the Raw Materials: As to the order of 

charging, the limestone is always charged first for these reasons: If it 
were charged on top of the scrap, for example, it would act as an insulator 
and thus prolong the melting period; it would all go to make up a part 
of the first slag, which would be too thick and viscous to work well; it 
would be drawn off with this slag in the run offs, thus leaving very little 
lime in the furnace to hold the phosphorus in the latter stages of the refine¬ 
ment; and, finally, the benefits to be derived from the lime boil, to be 
described later, would be lost. Upon the limestone, will be charged the 
ore, or briquettes, which, if any is needed, will vary in amount according 
to the nature of the rest of the charge and the heating capacity of the 
furnace. In order to hasten oxidation, ore may also be added from time 
to time during the later stages of the process. The scrap is next charged, 
and if cold pig iron is used, it is charged with the scrap. The gas, which is 
usually but partly turned on during the charging is then turned on full, and 
the first or melting stage begins. If hot metal is to be charged, it is not added 
until the melting period is well advanced. 

Melting Down the Charge: Heat is imparted to the charge partly 
through radiation from the incandescent particles in the flame. The fuel 
should, therefore, burn with a full long flame reaching almost from end to 
end of the furnace. But the flame should never extend through the ports 
and down-takes, as it would then rapidly fuse the brick of those 
flues and waste the fuel. For the same reason, the flame should 
be directed downward from the port and not be allowed to impinge on the 






PURIFICATION PEROIDS 


221 


roof. The light scrap and pig iron, if any is added to the solid charge, 
begin to melt first. During the melting much of these materials is oxidized, 
so that there is formed both molten metal and oxides, which trickle down 
over the scrap to the bottom. A slight amount of molten slag and metal 
is thus present, on the bottom of the furnace, before the hot metal, 
i. e., molten pig iron, is charged. Reversals of the flame should occur 
every fifteen to twenty minutes during this period, and care must be taken 
not to overheat the roof, for too high a temperature will cause the bricks 
in a new roof to spall, and those in an old one to fuse. Silica brick frequently 
sweat, that is, fuse slightly, but this condition does no harm and indicates 
a favorable temperature in the furnace. Care must be taken with the roof 
and checkers in a new furnace, especially, and the temperature must be 
kept relatively low for the first ten heats or more, after which time the 
gas may be gradually increased until the full working temperature is 
attained. 

The Addition of the Hot Metal: The molten metal can usually be 
added in about two hours after the charging of the solid materials is begun. 
The exact time for adding this metal is governed by the temperature of 
the solid charge. Evidently this temperature should be above, or at least 
as high as, that of the melting point for pig iron. This statement does not 
imply that the scrap, which has a much higher melting point than pig 
iron, should be completely melted. Indeed, a delay in the addition of the 
molten metal until the scrap is all melted may be very undesirable, for 
not only would the scrap be excessively oxidized, but the high temperature 
combined with the excess oxides present would result in a too violent 
reaction, and much foaming of the bath and loss of metal due to the rapid 
generation and evolution of carbon monoxide would result. 

The Purification Periods: The purification of the hot metal, after 
it is introduced into the furnace, is brought about through the oxidizing 
influence of the iron oxides and the fluxing properties of the limestone. 
While both oxidizing and fluxing reactions are actually taking place in the 
furnace at the same time, the action of the iron oxides must be considered 
as preceding that of the limestone, for the acid impurities must first be 
oxidized before they can be neutralized, or fluxed, by the bases. It is 
evident that the fluxing action may immediately succeed the oxidation, 
but the conditions set up by the manner of charging the limestone tends 
to retard its calcination and thus to separate the two actions. Now, the 
carbon monoxide generated by the action of the iron oxides upon the carbon 
of the pig iron is at first evolved in a manner quite different from that 
of the same gas formed later on in the process or of the carbon dioxide 
from the calcination of the limestone, and this difference is indicated by 
the way in which the bath is agitated. Hence, the fui nacemen have fallen 
into the habit of speaking of the purification as taking place in stages, 
known as the ore boil, the lime boil, and the working period. The third 




222 


OPEN HEARTH PROCESS 


is the stage that follows the complete calcination of the limestone. In 
order that the reader may understand what is implied by these terms, 
the changes that occur during the purification of the metal are discussed 
under these three headings. 

The Ore Boil: Proper chemical testing will show that the purification 
of the molten iron begins immediately after it is charged into the furnace, 
and, with the exception of carbon, the oxidation of which is not completed 
till the heat is ready to tap, progresses very rapidly. So, in about two 
hours practically all of the silicon and the greater part of the manganese 
will have been oxidized, and the former, then in the form of silica, will 
’ have been neutralized, some with lime, but the greater portion with the 
oxides of iron and manganese, and will have become slag. Some of the 
sulphur, also, will have been oxidized, particularly if the sulphur content 
of the hot metal was high, but as the oxides of this element are volatile 
and the high temperature tends to decompose the sulphites and sulphates, 
only a part of the oxidized sulphur is retained by the slag, and the remainder 
is carried off with the products of combustion. A very small portion of 
this element finds its way into the slag as sulphides, probably as manganese 
sulphide. With the silicon and manganese, the phosphorus is also rapidly 
attacked by the iron oxide, which not only oxidizes it, but neutralizes the 
resulting oxides of this element. These iron phosphates, which are easily 
reduced, likewise pass into the slag, where the iron oxide is replaced with 
lime, thus forming the calcium phosphates, which are very stable 
compounds. During all this time the carbon is also being slowly oxidized. 
This action, which at first takes place near the surface of the metal, results 
in the evolution of carbon monoxide in the form of tiny bubbles, which 
become entangled in the viscous slag and cause it to foam. Consequently, 
the slag, thus permeated with little gas cells, occupies much more than its 
natural space in the furnace. Carbon dioxide is also evolved by the lime¬ 
stone, which begins to be calcined more and more rapidly as the temperature 
at the bottom rises; but as the gas resulting from the decomposition of 
the limestone escapes in relatively large bubbles, it causes very little of 
the foaming. 

The Run off: When the slag level has been raised to a height a little 
above that of the bottom of the openings for the doors and is threatening 
to break through the dolomite dykes built up just inside these openings, 
the dolomite with which the slag hole is dammed is cleaned out of this 
opening, and the excess slag is allowed to flow through the cinder spout 
into the cinder pit or into a slag pot placed below to receive it. This 
tapping of slag is known as the run=off. The bases in this first slag 
are composed chiefly of iron and manganese oxides, the lime and magnesia 
being relatively low. It is not unusual for these slags to contain iron 
as oxide equivalent to 30% metallic iron, and as they constitute about 
40% of the total slag formed in the process, they represent the source of 
greatest loss of metal for the entire process. Practically all of the iron 
contained in the run-off is in the ferrous condition. 





PURIFICATION PERIODS 


223 


The Lime Boil: The action of the ore and other iron oxides, formed 
by the oxidizing flame, upon the carbon will be somewhat violent for two 
hours or more, during which time the scrap will have been almost com¬ 
pletely melted down. Gradually, however, as the carbon content decreases 
and the temperature of the bath rises, the ore boil subsides, or changes 
its character, and, the calcination of the limestone becoming more rapid, 
the lime boil is in the ascendency. The lime boil is characterized by a 
rising of the lime to the top of the bath and by a violent bubbling of the 
bath, caused by the rapid evolution of carbon dioxide gas from undecom¬ 
posed limestone which still remains on the bottom, and also in part by 
the continued oxidation of carbon in the molten metal. These activities 
play important parts in the process. Thus, not only does the violent 
bubbling caused by the evolution of the carbon dioxide gas agitate the 
metal and slag, thus mixing them and exposing the metal to the oxidizing 
influence of the flame, but a part of the gas, at least, unites, directly or 
indirectly, with the carbon remaining in the iron to form carbon monoxide. 
Furthermore, by rising to the surface, the lime may replace iron and 
manganese oxides in the phosphates, sulphates and silicates present and 
thus become a part of the slag, while any excess lime is also taken up and 
goes to increase the basicity of the slag. This property of the slag makes 
it more capable of retaining both the phosphoric and silicic acids together 
and renders the former less liable to be reduced. During this period the 
flame in the furnace should be reversed more frequently (about every 15 
minutes) in order that the temperature of the bath eventually will be well 
above the melting point of the decarbonized metal. 

The Working Period: Since all the impurities except carbon have 
now been eliminated, the operations during this period aim at regulating 
the properties of slag, adjusting the carbon content of the steel, and raising 
the temperature of the bath to the point where the steel may be tapped 
from the furnace and cast into ingots before it begins to solidify. In order 
for the steel to be teemed without difficulty, this temperature should be 
at least 167° C. (300° F.) above its fusion point. Both the chemical and 
the physical properties of the slag play most important parts in the basic 
process. In order that it may protect the metal against contamination 
by sulphur from the flame, retain the impurities, especially phosphorus, 
and promote the elimination of the carbon, the slag must contain a large 
quantity of active oxidizing agents, except at the end of the period, and 
must be strongly basic at all times. But even with the chemical com¬ 
position of the slag properly adjusted, its activity will depend upon the 
fluidity to a great extent. The reagents at the disposal of the operator 
for regulating these properties are iron oxide, limestone, dolomite and 
fluorspar. The iron oxide is usually in the form of lump ore, though heating 
furnace cinder formed on a magnesite bottom may be used. 

Methods of Working the Heat : There are two general 

methods of working heats, and briefly described, they are as follows: 



224 


OPEN HEARTH PROCESS 


The first method is somewhat like the Bessemer, that is, the carbon content 
of all heats is reduced to a common point, about .10%, when the steel will 
be tapped and the per cent, of carbon will be raised to that desired by 
the addition of recarburizers. In the second method the carbon is caught 
on the way down, that is, the carbon content is reduced to a point slightly 
under that required, to allow for the carbon contained in various additions, 
and the bath of steel is then tapped. Medium and low carbon steels are 
usually worked by the first method, while high carbon steels may be worked 
by either. 

Testing for Carbon: So toward the end of the lime boil, or earlier if 
it appears that the carbon content of the bath is dropping rapidly, the first 
helper will begin taking tests in order to follow the progress of the heat. These 
tests he takes by securing a small test-spoon full of the metal, which he 
pours into a small rectangular mould. As soon as the metal has solidified 
in the mould, it is removed by jarring the mould while in an inverted 
position; the test piece is nicked in the center, rapidly cooled with water, and 
then, while still warm enough to dry itself, it is broken with a heavy 
sledge hammer. From the fracture thus exposed, the. carbon content, 
which determines how the heat is to be treated, can be very accurately 
estimated. In order that the temperature of the bath may be raised to a 
point sufficiently high for tapping by the time the carbon is reduced to the 
point aimed at, it is desirable that the carbon content of the bath at the end 
of the lime boil should be forty to fifty hundredths of a per cent. (40 to 50 
points) higher than that desired at tapping. 

Control of Carbon and Temperature: If, as occasionally happens, 
the carbon is nearly all removed while the bath is yet too cold to tap and pour 
successfully, it is difficult, on account of its inactivity, to bring the heat 
up to the proper tapping temperature without danger of burning, or over¬ 
oxidizing the steel and unduly increasing the wear on the roof of the furnace. 
A heat working under such conditions is known as a sticker. To prevent 
this over-oxidizing, pigging up is resorted to, that is, the carbon content 
is held, or kept constant, by adding pig iron, which also aids in raising the 
temperature by producing a little boil in the bath. Usually, however, there 
will be fifty to eighty points of carbon to be removed from the bath after the 
lime boil. Therefore, as soon as the first helper sees that the lime is about 
all up, he will first take a test, then see that all lumps of unfused matter, 
or nigger heads, are melted and that the slag is sufficiently fluid. To 
bring about the rapid melting of the unfused bodies and increase the fluidity of 
the slag, fluorspar sufficient for the purpose will be added. Then to hasten the 
elimination of the carbon, it may be necessary to ore down, that is, additions 
of ore or heating furnace cinder will be made from time to time as required to 
reduce the carbon content. After each addition of oxide has had time to act, a 
test is taken. During the last half hour, in some cases the last hour, the heat 
is in the furnace, no ore will be added. Some foiemen erroneously believe that 
the elimination of carbon at this point may be hastened by stirring the bath 





WORKING THE HEAT 


225 


with a long steel bar, a process known as shaking down, while others 
will merely allow the metal to lie in the hearth undisturbed. In the case 
of low carbon heats the flame will now be reversed in the furnace about 
every ten minutes in order to raise the temperature, and as soon as the 
tests show that the carbon is within three or four points of the desired 
content, the melter, or foreman, is notified. He takes additional tests for 
the carbon content and also for temperature, orders the recarburizers, 
inspects the furnace, ladle, etc., and completes the arrangements for tapping 
the heat. 

Judging the Temperature of the Bath: For judging the temperature 
of the bath, two very simple tests are employed by the furnacemen. One 
of these tests consists of quickly inserting the end of a long steel bar or rod 
into the bath of metal and slowly moving it from side to side * until the 
part immersed in the metal melts off. Then the bar is withdrawn, and 
from the appearance of the hot end the condition of the bath with respect 
to temperature may be judged. Thus, if the bath is too cold, this end of 
the rod will be pointed; if too hot, it will show nicks on the sides near the 
end; but if the temperature is right, the end of the rod will have melted off 
so as to leave a clean, square end. The second method depends upon the 
quite evident fact that the higher the temperature of a fluid the longer 
it will remain fluid in contact with cold surroundings. It is carried out 
simply by quickly withdrawing a test-spoonful of the molten steel from 
the bath and at once pouring it, rather slowly, but at a fixed rate of 
flow, out of the spoon. The operator judges the temperature of the steel 
by the way it flows and by the extent and thickness of the skull it leaves 
in the spoon. By long practice with these methods the workmen become 
very expert in making these relative determinations of temperature. 

Tapping: The furnace should be manipulated so that a tapping tem¬ 
perature is reached before the carbon content has been reduced to the 
tapping point, as otherwise some difficulty will be experienced with high 
carbon steels in holding the bath, if the carbon is to be caught on the way 
down, while with low carbon steels, it will be difficult to reach a tapping tem¬ 
perature or the metal will be over-oxidized, with the result that it will tend 
to be both hot short and cold short unless deoxidizers such as spiegel, ferro¬ 
manganese, or pig iron, are added. Prolonging the life of the heat at this point 
in order to reduce the sulphur content is very bad practice for the double 
reason that the removal of the sulphur is uncertain and the cure is worse than 
the disease. The proper temperature for tapping low carbon heats is 1600° 
C., or a little higher, while for heats in which the carbon is caught on the 
-way down, the tapping temperature may be about 100° C., lower. To ac¬ 
complish the tapping, the second helper digs out from the rear the mud plug and 
most of the dolomite with which the tapping hole is closed, after which the hole 
is opened by driving outward the dolomite remaining in it by inserting a 
tapping rod through the wicket of the center door in the front of the furnace. 
The steel then flow's through the hole out of the furnace and down the 



226 


OPEN HEARTH PROCESS 


spout into the ladle. Since the tapping hole is on a level with the bottom 
of the hearth, the greater part of the steel is out of the furnace before any 
slag appears, and this fact permits of recarburization in the ladle. It is not 
advisable for the recarburizing materials to be allowed to come into 
contact with the slag, since some of the phosphoric acid in the slag may 
be reduced and the phosphorus re-enter the steel. The tapping spout and 
ladle are so placed as to direct the stream of molten metal a little to one 
side of the center of the ladle, as the swirling motion tends to mix and make 
more homogeneous the contents of the ladle. 

« 

SECTION V. 

FINISHING THE HEAT—MAKING STEEL FROM THE PURIFIED METAL. 

Methods of Finishing the Steel: The process of finishing the steel 
consists in making such additions as are required to produce the kind and 
grade of steel desired, and with few exceptions these additions are made 
immediately before and after tapping the heat. The methods of making 
the necessary additions to produce the various kinds and grades of steel 
differ somewhat, not only for the different grades but in different works 
making the same grades. For example, the ferro manganese and spiegel 
are preferably added to the steel in the ladle and in the molten state, but not 
all plants are at present equipped to melt these materials, and ferro manganese 
is still generally added in the solid form. For the plain steels the methods of 
making additions for carbon and manganese may be briefly stated in the 
following tabulated form. 

High Carbon Steels. (C.60% to 1.30%) 

Method I. Carbon is caught on the way down; ferro-manganese 
is added, and coal, if needed, in the steel ladle. 

Method II. The steel is tapped with the carbon at .10%; molten 
spiegel mixture is added in the steel ladle. 

Method III. The carbon in the bath is eliminated to .10%; sufficient 
molten pig iron is added in the furnace at the time of tapping to raise the carbon 
content almost to the point desired. Then ferro-manganese may be added to 
the ladle to make up the deficit in the carbon, and supply the manganese 
deficit left by the pig iron. 

Medium Carbon Steels. (C. .30% to .70%) 

Method I. The steel is tapped with a carbon content of .10%; molten 
spiegel mixture is added in the steel ladle. 

Method II. The carbon in the bath is eliminated to .10%; molten pig 
iron is added in the furnace and ferro-manganese in the ladle as in III for high 
carbon steels. 

Low Carbon Steels. (C. less than .40%) 

Method I. For dead soft steels the carbon content is reduced as low 
as possible without danger of over-oxidizing the steel, and ferro-manganese 
is added in the steel ladle. 




FINISHING THE HEAT 


227 


Method II. The carbon content is reduced to .10% and ferro-manga- 
nese is added alone, or ferro-manganese and coal are added in the steel 
ladle. In case a large quantity of ferro is required, some furnacemen 
prefer to add a part of it in the furnace just before the tapping hole is opened. 

Method III. For finishing very low carbon steels neither molten spiegel 
nor molten pig iron are used on account of the difficulty of weighing and keep¬ 
ing molten small quantities of these materials. But in large furnaces, pig 
iron maybe used, if the carbon content is more than .20%, as in Method II for 
medium carbon steels. 

Other Elements: The additions for other elements will be made about 
as follows:—Copper is added in the solid form to the steel fifteen to twenty 
minutes before the heat is tapped. Sulphur is always added before the ferro 
additions. Ferro silicon is necessarily added in the steel ladle; while it is the 
common practice to add ferro vanadium by dropping it into the stream of 
molten metal in the runner, or spout, as it is flowing into the ladle. As 
nickel is chemically negative to iron, none is lost in the furnace, so nickel steels 
are made by charging nickel steel scrap, then adding pig nickel in sufficient 
amount to make up the deficiency, as shown by chemical analysis, about 
thirty or forty minutes before tapping. The same practice may be 
employed in the case of steel requiring copper and chromium, but a 
comparatively large part of the latter element is lost through oxidation 
in the furnace. Chromium is added in the form of ferro chromium. 

Some Features that Make the Finishing of the Steel Difficult: It 

requires considerable experience to finish steel properly, for there are a 
number of circumstances that tend to complicate the operations. For 
example, the addition of ferro, on account of its carbon content, will always 
slightly raise the carbon content of the steel, though it is primarily added 
to increase the manganese. Similar conditions also prevail in the use of 
other ferro alloys and pig iron. Again, there is always a loss of the 
elements added, except in the case of copper and nickel, and this loss, 
different for each element, will vary with any one under different con¬ 
ditions. Hence, the efficiency of these substances is never 100%. Furthermore, 
it is seldom any of the elements can be obtained in pure form for this purpose, 
and the substance containing the element sought may vary in its content of 
that element. The various substances used, their efficiencies, and the amount 
of each element present in the bath at the tapping of a normal heat are 
indicated in the following table. 



228 


OPEN HEARTH PROCESS 


Table 31. Data Relating to Materials Used in Finishing Steel. 


Material Added 

Element 

Sought 

Percentage of Element 
in Bath 

Efficiency 

When Added in 

Furnace 

Ladle 

Pig Nickel... 

Ni 

.00 unless Ni. scrap used 

98% 

Never 

Ferro Chromium. 

Cr 

.00 “ Cr. “ 

80% 

• 4 

Pig Copper. 

Cu 

.00 “ Cu. “ 

99% 

4 4 

Stick Sulphur. 

S 

.040 

Never 

66%—70% 

Anthracite Slack. 

c 

Any desired 

4 4 

44%—50% 

Pig Iron. 

c 

44 

95% 

Never 

44 

Mn 

.10 to .20 

50% 

4 4 

Ferro Manganese. 

Mn 

.10 to .20 

50% 

85%—90% 

Spiegel. 

Mn 

.10 to .20 

Never 

S0%—90% 

« 4 

C 

.10 to Any desired 

44 

100% 

Ferro Phosphorus. 

P 

.010 

1 t 

75% 

Ferro Silicon. 

Si 

.00 

( < 

65—70% 

Ferro Vanadium. 

V 

.00 unless V. scrap used 

« t 

) 

90% 


In the following table will be found an analysis typical of each of these 
substances. 

Table 32. Representative Analyses of Materials Used in Finishing Steel. 



Fe 

% 

C 

% 

Mn 

% 

P 

% 

S 

% 

Si 

% 

V 

% 

Cr 

% 

Ni 

% 

Cu 

% 

Ferro Manganese. 

13.03 

6.80 

79.35 

.16 


.66 





** Phosphorus. 

79.97 

1.10 

.18 

18.00 

.65 

.10 


. d. . 



“ Silicon, Electric. 

49.44 

.55 

.016 

.075 

.018 

49.90 





“ Blast Fee. 

87.465 

1.52 

.42 

.080 

.015 

10.50 





“ Chrome. 

22.05 

6.36 

.35 

.003 

.79 

.48 


69.96 



“ Vanadium. 

42.65 

1.58 

6.25 

.010 

1.06 

10.49 

37.96 




Spiegel. 

75.68 

4.39 

19.13 

.053 

.028 

.72 





Pig Nickel. 









97.00 


Pig Copper. 









99 00 

Stick Sulphur. 





100.00 






Pig Iron. 

94.00 

3.80 

1.00 

.17 

.030 

1.00 






Given the weight and composition of the metal in the bath, the desired 
composition of the finished steel, and the composition and efficiencies of the 
substances to be added, the calculation of the amounts of the various additions 
is a simple problem in arithemetic. 

Teeming: As soon as the stream from the furnace no longer contains 
any steel, the spout, or runner, is removed, and the steel ladle is lifted by 
the crane and carried to the pouring platform, where the steel is teemed 
into the ingot moulds ready to receive it. Teeming is not to be confused with 
pouring. While the latter logically refers to the way the metal is let out of 
the ladle, usage has made pouring synonymous with casting,which refers to the 
manner of introducing the metal into the ingot mould. Thus, if the metal 









































































TEEMING AND SAMPLING 


229 


is introduced into the mould through its top, the resulting ingot is said to have 
been top poured or top cast; but if through its bottom by means of runners, 
the ingot is said to have been bottom poured or bottom cast. Teeming and 
top pouring are accomplished in the following manner: The ladle is pi aced with 
its nozzle over the center and about a foot from the top of the first mould in the 
mould train, when the stopper is raised and the steel flows through the 
nozzle into the mould below. In teeming the heats, care must be 
taken that neither the stream of metal nor any part thereof be allowed 
to strike the sides of the moulds, for these splashes of metal will adhere 
to the mould, which quickly chills them, and, being coated on their surfaces 
with a film of oxide, they may cause ingot defects which later appear as 
slivers in the rolled steel. As the first mould is filled, the stream is stopped, 
and by means of a hydraulic pusher the train is moved forward so as to 
bring the next mould under the nozzle of the ladle. At some plants the 
teeming is done from an overhead crane, which moves the ladle from mould 
to mould. After the ladle has been emptied of steel, the slag remaining 
in it is dumped into cinder cars and ultimately conveyed to the cinder yard. 
In the meantime, the mould train is hauled to the stripper. On soft steel 
and special heats, unless there is a high percentage of manganese or silicon 
present, aluminum is thrown into the moulds, about two ounces to each ton, 
in order to further deoxidize and quiet the steel. Aluminum is especially 
effective in overcoming wildness because of its strong tendency to combine 
with oxygen. Of this small amount added practically none remains in the 
metal, so that this aluminum exerts no influence as an alloy in the steel. 

Sampling: The sampling of the heat for chemical analysis is accom¬ 
plished when the heat is half teemed by slackening the stream from the 
ladle, whilst a spoon of suitable size is held under the nozzle and filled with 
the molten metal, which is immediately poured into a test mould specially 
designed for the purpose. The test mould may be of either one of two 
types, which careful and extensive experiments have shown to give test 
pieces most uniform in composition and most free from blow holes. One 
of these types is a split mould that gives a test piece having a section 1 A. 
inches square and a length of nearly 5 inches, with a flared opening about 2 
inches deep to facilitate pouring. The other type is a small cup shaped 
mould that gives a test piece 3 % inches in diameter at the top and 2 l A 
inches at the bottom with a depth of 2Jh£ inches. Upon being taken from 
the mould, the test piece is immediately stamped with its heat number, 
and is then delivered to the chemical laboratory for analysis. Experiments 
have shown that a sample taken in this way most nearly represents the 
average composition of the heat. 

SECTION VI. 

KEEPING THE FURNACE IN REPAIR. 

Preparation of the Furnace for the Next Charge: After the runner 
is lifted and thus detached from the furnace, the cinder and any steel that 
remains in the furnace flow out of the tapping hole into the cinder pit. 





230 


OPEN HEARTH PROCESS 


The second helper must keep the tapping-hole open until everything that 
can be removed from the furnace has flowed out. Fluorspar is usually 
thrown in on the slag left to be sure that it flows out and does not build 
up on the bottom of the furnace. Often, holes will be found in the bottom, 
due to the intrusion of steel below the surface, which, boiling there, brings 
up part of the basic material forming the bottom. Slag and steel are found 
in these holes after tapping and must be rabbled out, so that the bottom 
can be properly repaired. After all the steel and slag are removed from 
these holes, they are filled up with dolomite. The gas is left on to keep 
the slag and steel fluid during this process; but is shut off as soon as the 
repairs to the bottom have been completed. Proceeding to the next step, 
the second helper and cinder-pit man remove the steel that has chilled in 
the tapping hole, rake out and free the hole of iron and close it up with 
dolomite. A plug of clay is used to seal up the outside of the hole and hold 
the dolomite in place. The banks, which have been cut by the slag from 
the heat just out, are repaired by throwing burned dolomite on them (3000 
to 4000 lbs. is used after each heat in a 100-ton furnace); and the furnace 
is then ready for charging again. 

Furnace Troubles: In the operation of a furnace, troubles of a very 
serious nature may occur at anytime, unless the furnace is watched closely, 
and carefully handled. These troubles present so many possibilities and 
are so varied that space will permit of little more than an enumeration 
of some of the more serious ones here. Thus, the tap-hole may break out 
prematurely if it is not properly tamped and capped, or it may become 
hopelessly clogged if it is not properly cleaned after each heat. Sometimes, 
sections of the bottom become detached and rise, due to the buoyant force 
of the metal, and when this occurs the heat must be tapped at once, and 
no more heats may be charged until the damaged bottom is repaired. The 
ports require constant attention to prevent them from building up or melting 
down, and thus changing the angle of the flame, which would then tend to 
over-heat some part of the furnace and would be rendered less effective 
in heating the bath. Leaks may occur in the walls of the up-and-down- 
takes, which result in the gas being burnt in part before it reaches the 
hearth. The walls and roof often wear out long before the rest of the 
furnace needs repairing. Roofs usually last for about 300 heats. The roof 
can be repaired in a few hours, and a cave-in of the roof is of a serious 
nature only when it falls in near the end of a heat. The most disastrous 
mishap that can occur to a furnace is a break-out. Breakouts may be 
caused by several things. A hole near a bank may not have been noticed 
or may have been insufficiently repaired, in which case the steel works 
down into it and gradually makes it deeper, until, finally, the metal finds 
its way through the wall and out of the furnace. Sometimes, owing to a 
thin spot on the banks or to slag having reached above them and worked 
down into them, the slag gradually cuts its way out through the walls, in 
which case it is usually followed by steel, as the hole soon becomes low 
enough to reach the bath. Such mishaps are also known as break-outs 





FURNACE REPAIRS 


231 


and are always of a serious nature. Once a break-out occurs, the tapping 
hole should be opened immediately, and as much as possible of the steel 
gotten into the ladle or cinder pit. The spread of cinder and metal upon 
the floor where the break-out has occurred can be limited usually by 
throwing dolomite around it. Finally, after about 600 or 700 heats, the 
checker work has become so badly clogged and the brick work is so eaten 
away, that it becomes necessary to close down the furnace for general 
repairs, during which the greater part of the brick work may be torn out 
and rebuilt. 

Repair Materials: It is evdent that, for making up the bottom and 
for doing the repair work about a furnace, much depends upon the materials 
employed. Great care must always be exercised to see that they are of 
the right chemical composition, and best suited for the work in hand, as, 
otherwise, the best of workmanship in making the repairs will go for naught. 
Therefore, a few remarks in this connection should be of interest. 

Dolomite is found in local deposits similar to those of limestone. Like 
the latter it varies in composition through quite wide ranges, but that 
suitable for open hearth work will have, after being calcined, approximately 
the composition shown by the following chemical analysis: Silica, Si 02 ,. 
1 . 66 %; Iron Oxide, Fe 20 s, .94%; Alumina, AI 2 O 3 , 1.24%; Lime, CaO y 
50.01%; Magnesia, MgO, 35.26%. 

Magnesite: The magnesite used before the European war was im¬ 
ported from Madelein and Budapest, Austria, and was brought to the mill 
already burned and ground. It was used on the furnace bottom, banks and 
ports, and in repair work. An average analysis of thirty-eight cars of the 
imported material is as follows:— 

Si 02 Fe Mn AI 2 O 3 CaO MgO Ig.Loss 

2.07% 6.00% .37% 1.63% 3.81% 84.11% .52% 

Since the outbreak of the war, however, deposits of this material in 
California and Washington have been opened, and this domestic supply 
promises to replace permanently the imported material. This magnesite is 
purer than the imported, and for that reason it does not sinter or bond so 
readily, but by mixing a little of the proper fluxing material with it, this 
drawback has been easily overcome. 

Chrome Ore: Chrome ore is still imported, as the limited deposits 
so far discovered in the United States and Canada are of an inferior grade. 
It is received in the form of small lumps. It is ground and mixed, in a wet 
pan, with one-half magnesite, and is used in repair work where a neutral 
substance is required, such as in patching flues, tapping holes, ports, etc. 
An analysis of an average sample of a satisfactory grade of this ore gave 
these results: 

Si0 2 FeO MnO A1 2 0 3 MgO Cr 2 0 3 Ig. Loss 

9.02% 13.50% .80% 10.82% 19.89% 42.66% 2.92% 



232 


OPEN HEARTH PROCESS 


Besides these materials, some ganister may be employed at some of the 
works, while all plants will use large quantities of loam and of fire clay for 
lining furance spouts and ladles, for making up stoppers, and for other 
repair work of minor importance. 


SECTION VII. 

CHEMISTRY OF THE BASIC PROCESS. 

Some of the Principles and Conditions Involved: Having followed 

the procedure of making steel by this process, the reader should be interested 
in a discussion of a subject, which to the metallurgist, at least, represents 
the most interesting and profitable part of the study, namely, the chemistry 
of the process. In beginning this study it should be recalled that the 
purification of pig iron, which is the first of the two main steps in making 
steel, includes the elimination from the metal of the four elements, silicon, 
manganese, phosphorus and carbon, and that the principle by which this 
elimination is effected is that of oxidation. In basic open hearth processes, 
the elimination of sulphur may also take place to a greater or less extent, 
depending upon the amount present, but is never to be considered seriously 
as a principal objective. It now remains to be pointed out that this 
oxidation, when brought about indirectly, that is, through the interaction 
of these elements with oxygen bearing compounds, as is the case in this 
process, involves two other principles as well. These are the principles 
of reduction and neutralization, for it is manifestly impossible under these 
conditions that one substance can be oxidized without another’s being 
reduced, and it develops, as will be shown later, that this interaction is 
made possible through the immediate neutralization of the oxidized sub¬ 
stances. While these principles and the reactions by which the purification 
is brought about are, when considered separately, very simple and can be 
easily understood, they are somewhat difficult to follow in the actual 
working of the furnace, because they are here occurring simultaneously 
and, therefore, tend to mask each other in the effects they produce. For 
this reason it is best to consider the subject, first, from the standpoint of 
the chemical properties of the elements affected and of the oxygen com¬ 
pounds of these elements under the conditions of the basic open hearth 
process. 

Properties of Iron and Its Oxides: One of the most marked of the 
chemical properties of metallic iron is its tendency to combine with oxygen. 
Even at ordinary temperatures this tendency is very marked, as is seen 
from the ease and quickness with which it combines with oxygen and water 
to form the familiar compoimds known commonly as iron rust. These 




CHEMISTRY OF THE PROCESS 


233 


compounds are but the hydrated sesqui-oxide, or per-oxide, of iron contain¬ 
ing varying amounts of combined water, as represented by the formula 
Fe2C>3*xH20. This tendency of iron and oxygen becomes stronger as the 
temperature rises, so that at a temperature ranging from 800° to 900°, or 
higher, the combination becomes very rapid, and a compound quite different 
from those composing rust is formed. It is commonly known as Scale, 
and is represented by the formula Fe3(>4, or FeO*Fe203. These facts help 
to explain why iron is seldom found in nature uncombined, and the two 
compounds, represented by the formulas given above, together with the 
carbonate of iron, constitute the valuable part of all the ores of iron. The 
ore used in all our furnaces is the red hematite, which for the purpose of 
this discussion, may be considered as being composed of the sesqui-oxide, 
Fe203, and gangue. Besides free oxygen, certain compounds may, at high 
temperature, serve as sources of supply of oxygen to iron. Among these 
are carbon dioxide and water vapor, which constitute the chief products 
of combustion in any case of burning a fuel in the presence of an excess of 
oxygen, such as normally exists in an open hearth furnace. The heating 
of free iron to these high temperatures in contact with either free oxygen 
or steam always results in the formation of Fe3C>4, according to the following 
reactions:—3Fe+202=Fe304, 3Fe-j-4H 2 0=Fe304-l-4H2. But at a tem¬ 
perature of 1000°C. or more, with iron in contact with carbon dioxide, another 
and less common oxide, FeO is formed, thus Fe+C02=FeO+CO. Ferrous 
oxide, FeO, and ferroso-ferric oxide, Fe304, may be formed in the furnace 
in other ways, also, one of which is by the progressive reduction of Fe203- 
If Fe203 be heated to a high temperature it loses oxygen and is converted 
into Fe304. This change takes place at temperatures between 1100° and 
1200° C., some 500 degrees below the maximum temperatures of the open 
hearth. If FeO be formed under conditions even only slightly oxidizing, 
it passes into Fe304. Another difference in the properties of these oxides, 
which is of great importance in considering the chemistry of the open hearth, 
is seen in their power to neutralize acids. Thus, while both Fe203 and FeO ex¬ 
hibit very marked basic properties and combine rapidly with acid oxides, 
Fes04 cannot be induced to form corresponding salts at the temperatures that 
prevail in the open hearth. Pure scale, Fes04, fuses at about 1450° C., a temper¬ 
ature easily attainable in the open hearth, and it dissolves readily in either 
iron or calcium silicates. Ferrous oxide, FeO, is soluble in both the molten 
iron and the slag, and though the amount that remains dissolved in the metal 
when solid is small, being seldom present to an extent greater than .315% 
the equivalent of .07% oxygen, its effects are very harmful, as it produces 
both red and cold shortness in the metal. With metallic manganese it gives 
the following reaction: FeO + Mn=Fe-f-MnO. MnO is not soluble in the 
molten metal, which fact assists in accounting for the efficiency of manganese 
as a deoxidizing agent. 

The Importance of Ferrous Oxide, FeO, in the Part Played by the 
Oxides of Iron in the Process: From what has been said concerning the 
properties of the three oxides of iron, it is evident that ferrous oxide, FeO. 




234 


OPEN HEARTH PROCESS 


is the principal, perhaps the only, direct oxidizing agent in the open hearth 
process. Although iron sesquioxide, Fe 2 C> 3 , may be charged into the 
furnace, much of this oxide is transformed by the heat into ferroso-ferric 
oxide, Fe 3 C> 4 , before it has an opportunity to become active. Besides, 
since the impurities are held in solution by the metal, either the oxidizing 
agent must dissolve in the metal, a condition that is not true for either Fe304 
or Fe 2 C> 3 , or the oxidation of the impurities must occur at the surface of contact 
between metal and slag. That conditions in the open hearth during the melt¬ 
ing period tend to form an abundant supply of ferrous oxide can be shown by 
an analysis of the first slag formed, as is illustrated by the following analyses 
of samples of this slag taken just before the introduction of the hot metal. 


Table 33. Analysis of First Slag Formed in 
Open Hearth Heats 



Si0 2 

% 

FeO 

% 

Fe 2 03 

% 

MnO 

% 

p 2 o 5 

% 

A1 2 0;j 

% 

CaO 

% 

MgO 

% 

S 

(S+S0 8 

% 

Slag from Fee., 

No. 9. 

8.54 

61.05 

11.10 

2.31 

.26 

1.98 

9.13 

5.48 

.16 

Slag from Fee., 










No. 15. 

1.00 

78.24 

15.31 

.81 

.14 

.37 

2.70 

1.12 

.25 


Concerning the neutralizing powers of these oxides, FeO must also act 
as the initial base, as will be shown later, but in the slag Fe 203 is also 
capable of acting as a base. It is important to emphasize these facts here 
because of their influence on the chemical action of the other elements 
eliminated during the purification period, for their action depends on the 
conditions, which it is, therefore, essential to define. Briefly, the chief of 
these conditions is that at the time of introducing the hot metal there is 
present in the furnace a slag that is very rich in ferrous oxide. 


Properties of Silicon and Its Oxide, Silica: Silicon forms but one 
compound with oxygen under the conditions prevailing in the open hearth, 
and this compound is silica, Si02- The tendency of silicon to combine 
with oxygen is even stronger than that of iron, due to the greater heat of 
formation of its oxide, so that it is capable of reducing any of the oxides 
of the latter, and upon this fact depends the elimination of this element 
from the molten metal. As to which of the oxides of iron is the active 
agent in the oxidation of silicon, there can be little doubt but that ferrous 
oxide, FeO, is the principal one that suffers direct reduction by the silicon, 
for, as already indicated, the silicon, either as an alloy or a compound of 































CHEMISTRY OF THE PROCESS 


235 


iron, is distributed throughout the mass of molten metal, and it is necessary 
that either the oxidizing agent also dissolve in the liquid or the silicon diffuse 
to the surface of the metal in order that the molecules may be brought into that 
intimate contact required to effect a reaction. The oxidation of the silicon, 
then, is represented by the following reaction: Si+2FeO=SiC>2+2Fe. 
Silicon, however, is a very strong acid, so that if this reaction occurs, the silica 
will immediately combine with ferrous oxide to form a bisilicate, a tri-silicate 
or some still more acid salt, depending upon the relative amount of base 
available. Since this oxidation takes place with only a limited supply of ferrous 
oxide present, it may be assumed that the salt requiring the least base, such as 
the tri-silicate, would be formed. If so, the reaction would be as follows: 
3 Si02+-2Fe0=(Fe0)2*(Si02)3. If the bisilicate is formed, the reaction 
would be represented thus: Si0 2 +FeO=FeO Si(> 2 . Since the neutral¬ 
izing action must always instantly follow the oxidation, it is perhaps best 
to represent the change by a single reaction, which can be done by com¬ 
bining the first two, thus: 3Si+8FeO=(FeO)2' (Si0 2 )3+6Fe. The ferrous 
silicate is in the fluid state, for its fusion point is below that of the metal. 
It is of lower density than the iron, and, therefore, rises to the surface, 
where it temporarily forms a part of the slag. On the way to the slag it 
may undergo a change as noted later under manganese. Once in the slag, 
this ferrous silicate is capable of undergoing many changes. The first of 
these changes is probably due to the ability of the silica to take on additional 
base. Having been formed in a region where there is only a limited supply 
of base, the silica could not be neutralized to the extent it is capable. But 
now, having diffused into the slag, where there is abundance of bases, this 
trisilicate may become a monosilicate with either a monoxide or a sesqui- 
oxide base. The formation of the monosilicate with the monoxide base, 
FeO, may be represented thus: (Fe0) 2 *(Si02)3-f-4 FeO=3(FeO)2 - SiC>2, 
The ferrous oxide thus combined cannot act as an oxidizer and, therefore, 
becomes inactive. However, it may be made available through the action 
of lime and magnesia. Both these bases are capable of replacing ferrous 
oxide in the manner indicated by the following reactions:— 


(Fe0) 2 -Si0 2 + 


/2 CaO _/CaO ) 2 -Si0 2 
\2 MgO - \Mg0) 2 -Si0 2 


The ferrous oxide thus liberated is now subject to reduction, and available 
to the bath for further use. The sources of supply of lime and magnesia 
are the stone charged into the furnace and the lining of the furnace itself. 
These alkaline earth silicates constitute the major portion of all the final 
slags formed in the process, but these slags are never free of iron, for they 
hold its oxides in solution. 

Properties of Manganese and Its Oxides: While manganese com¬ 
bines with oxygen in several different proportions to form an equal number 
of different oxides, under the conditions that exist in the basic open hearth 
only one of these oxides is formed, namely, the manganous oxide, or 
protoxide of manganese, MnO. Like silicon, the manganese in the charge, 






236 


OPEN HEARTH PROCESS 


being alloyed with iron,must be oxidized largely through the agency of ferrous 
oxide. But as silicon is capable of reducing manganese oxide, there appears 
little chance of oxidizing the latter until the former element has been largely 
eliminated from the bath. However, there is much evidence to show that 
at least a part of the manganese finds its way into the slag long before all 
the silicon has been oxidized. This fact is explained by the assumption 
that manganese is capable of replacing iron in the silicates of iron, thus: 
FeO•Si0 2 +Mn=MnO' Si0 2 +Fe.or (FeO) 2 - (Si0 2 ) 3 +2Mn=(Mn0) 2 * (Si0 2 ) 3 
+2 Fe. With this idea in mind, it is easy to conceive the simul¬ 
taneous elimination of both these elements, in which elimination the ferrous 
oxide plays the part of oxidizing agent, only, and manganese fulfills the 
office of the base for the neutralization of the silica. Such a change, 
involving the simultaneous oxidation of silicon and manganese, is represented 
by the following reaction: 3 Fe0+Si+Mn=Mn0*Si0 2 +3Fe. When this 
silicate of manganese reaches the slag, it is subject to the same changes as 
are the corresponding iron oxide silicates, the manganese oxide being 
eventually set free by lime and magnesia. This free oxide of manganese, 
being insoluble in the metal, remains in the slag as such as long as the 
latter is rich in iron oxides; but if the slag should be depleted of its oxides, 
then manganous oxide is liable to reduction, in which event the resulting 
metallic manganese returns to the bath. Another property of manganese, 
though it is of little importance in ordinary open hearth operations, may 
be mentioned. It refers to the ability of manganese to replace iron in 
combination with sulphur. Thus, all the sulphur contained in the pig iron 
or steel scrap going into the furnace may be considered as being combined 
with this element and in the form of manganese sulphide. This substance 
is slightly soluble in the slag as well as in the metal, and this fact accounts 
for the presence of small amounts of sulphide found in open hearth slags. On 
the surface of the slag, incontact with an oxidizing flame, manganese sulphide 
is subject to oxidation according to this reaction: 2 MnS+30 2 =2 MnO-f- 
2 S0 2 . The sulphur dioxide, S0 2 , thus formed is a gas and may escape from 
the furnace with the products of combustion. However, it is evident that 
the quantity of sulphur removed in this way must be very small. 

Sulphur and Its Oxides: Owing to the peculiar properties of sulphur 
and its oxides, they are subject to a number of conflicting influences, under 
the conditions of the open hearth process, that render the removal of this 
element very uncertain. As an element, sulphur combines directly with 
iron to form iron sulphide and is easily oxidized to form oxides, S0 2 and 
S0 3 , both of which are gaseous acid anhydrides, and, when neutralized, 
form sulphites and sulphates, respectively. At temperatures far below the 
iowest working temperature* of the open hearth, the sulphites and sulphates 
of the heavier metals, like iron, for example, decompose to form either the 
sulphide or the oxide of the metal and sulphur dioxide. At temperatures 
relatively low for furnace operations, like that of the puddling furnace, both 
manganese and iron sulphides are readily oxidized by the higher oxides of 




CHEMISTRY OF THE PROCESS 


237 


these elements, such as Fe 2 0 3 , forming oxides of the metals and S0 2 which 
escapes, as a gas, from the furnace. At the higher temperatures of the open 
hearth there are a number of factors that operate against the elimination 
of the sulphur in this way, among which may be mentioned an increased 
tendency of iron to combine with sulphur, an increase in the reducing power 
of the molten iron, the fact that CO gas is capable of reducing S0 2 , and the 
probability that there is little Fe 2 0 3 available to do the work. Fe 3 04 
may replace Fe 2 0 3 in the oxidation, but it is very improbable that FeO 
is capable of producing the same result. Unlike the sulphates of the heavy 
metals, the sulphates of the alkaline earths, such as calcium sulphate, are 
not decomposed by heat alone, at least not by any temperature attainable 
in the open hearth. Therefore, once the sulphur is oxidized and thus com¬ 
bined with lime, there is some chance of its being held by the slag. How¬ 
ever, iron is capable of decomposing the sulphate of lime, thus, CaS 04 -(- 
4 Fe=FeS-l-CaO-{-3 FeO, in which case the iron sulphide dissolves in the 
iron. As evidence that such a reaction may take place, several instances 
may be cited in which steel has been ruined, for the order it was intended, 
through charging old boiler tubes, containing much boiler scale, with the 
scrap. The presence of oxides in the slag tend to hold this reaction in 
check, so that it takes place to an appreciable degree only when the slag 
is burdened with an excessive amount of this sulphate, and even then it 
can occur only at the surfaces of contact between metal and slag. 

Sulphur From the Fuel: Another source from which sulphur may be 
imparted to the metal is the fuel. That fuel carrying compounds of sulphur 
may be responsible for a portion of the sulphur content of steel is a well known 
fact, but through what reactions the transfer is brought about does not appear 
to have been satisfactorily explained. Now, it has been established by J. 
B. Ferguson, writing in the Journal of the American Chemical Society, Novem¬ 
ber, 1918, that “CO andS02 react between 1000°C. and 1200°C. to form CO 2 
and sulphur vapor and traces of carbon oxysulfide in mixtures rich in CO.” 
In the early stages of an open hearth heat, just after the addition of the molten 
pig of the charge, these conditions as to temperature and presence of CO gas 
prevail at the surface of the charge, and any sulphur vapor that may be formed 
as above will readily be taken up by the exposed molten or solid metal of the 
charge, forming iron sulfide. If there is taken into account the action of man¬ 
ganese toward sulphur, there are, then, two agencies that act feebly to eliminate 
sulphur from the metal, and two that are active, also feebly, in returning 
it, or of introducing it. The stability of the calcium sulphate, however, 
acts as a guard against the introduction of the element, except under some 
such unusual condition as that noted above. 

ir 

Phosphorus and Its Oxides: This element is very easily oxidized, 
when in the free state, by oxygen alone, and forms several oxides, of which 
only one, phosphorus pentoxide, P 2 Os, need be considered here, because it 
is the only one formed under the conditions prevailing in the open hearth. 
Like sulphur, phosphorus occurs in the metal as a definite compound, iron 





238 


OPEN HEARTH PROCESS 


phosphide, Fe 3 P, and like silica, the oxide, P 2 O 5 , is an acid, which must 
be neutralized as soon as it is formed. The reaction by which it is removed 
from the metal is, therefore, probably most nearly correctly represented 
by the following expression: 2 Fe 3 P +8 Fe 0 =(Fe 0 ) 3 -P 205 +ll Fe. Silica 
has the power of replacing P 2 O 5 in the ferrous phosphate, thus exposing the 
latter oxide to reduction, so that phosphorus is never permanently removed 
from the metal until the silicon has been practically all eliminated. This 
power of silica also accounts in part for the fact that phosphorus is not 
eliminated by any of the acid processes for making steel, for the proportion 
of this compound in the slag effectually prevents the formation of the 
phosphate. In the basic process the abundance of bases present in the 
slag is more than sufficient to satisfy the silica, so that the ferrous phosphate 
is not only permitted to form, but on reaching the slag it is converted 
into a much more stable calcium phosphate, probably the tri-calcium 
phosphate, (Ca 0 ) 3 *P 20 5 . Even this salt is, relatively speaking, easily 
reduced. Phosphorus, therefore, is held by the slag only so long as the 
latter is maintained strongly basic and at least moderately oxidizing. 

Carbon and Its Oxides: Owing to the peculiar chemical and physical 
properties of carbon and its oxides, the elimination of this element gives 
rise to phenomena distinctively different from those of the elements just 
reviewed. In that review it was pointed out that the oxidation of those 
elements gives compounds which are liquids under the conditions of the 
open hearth, that is, they are slag forming elements. But the oxidation 
of the carbon, which is represented by the reactions C+FeO=CO+Fe and 
Fe 3 C+FeO=CO-l-4 Fe, gives rise to the gas carbon monoxide, and, owing 
to the conditions under which it takes place, produces the phenomenon 
known as the ore boil. Thus, since the carbon, either as a compound or 
as an element, is dissolved in the metal, and the iron oxides, in the slag, 
the region of greatest activity, at the beginning of the oxidation, is located 
near the surface of contact between the two liquids. The generation of 
the carbon monoxide here gives rise to innumerable tiny bubbles of the 
gas, which immediately rise into the slag; but owing to the small size of 
the former and the viscosity of the latter, their immediate escape is 
hindered, so that they find their way to the surface very slowly. They 
thus collect in the slag, increasing its volume and imparting to it the appear¬ 
ance of foam. In the course of time, the highly oxidizing condition of the 
bath has disappeared with the consequent lowering of the carbon content, 
and both oxide and carbon are so reduced in amount that the oxidation 
no longer takes place rapidly and near the surface of the metal; so the slag 
loses the foamy appearance. Indeed, as the silicon, manganese, phosphorus 
and part of the carbon have been oxidized, the bath of metal is becoming 
depleted of its reducing agents, so that more and more ferrous oxide pene¬ 
trates or is dissolved by the metal, which fact, together with the decom¬ 
position of the limestone, gives rise to the formation of large bodies, or 
bubbles, of carbon monoxide deep down in or near the bottom of the layer 





CHEMISTRY OF THE PROCESS 


239 


of metal. These bubbles rise through the metal rapidly, so that when they 
strike the slag, it is not given time to part, but is lifted into the atmosphere 
of the furnace and thrown to one side. 

The Action of the Limestone: It is interesting to note to what 
extent the decomposition of the limestone on the bottom of the furnace 
may contribute to this action and to the elimination of the carbon. The 
reaction representing this decomposition is CaC 03 =Ca 0 -|-C 02 . Now, the 
carbon dioxide gas is no sooner set free than it is attacked by iron, thus: 
C02-fFe=Fe0+C0. The FeO is then available for the oxidation of the 
carbon in the metal, thus: FeO+C=Fe+CO. By combining these two 
reactions it will be observed that, from each and every volume of carbon 
dioxide, CO 2 , liberated, two volumes of carbon monoxide, CO, result. The 
CO derived from the decomposition of the limestone, as well as that from 
the action of dissolved FeO, escapes to the surface as just described. Any 
ore that might have remained at the bottom of the furnace up to this period 
of the carbon elimination would also contribute to the violence of this 
action. At the surface of the slag the carbon monoxide discharged by 
the bath may burn to carbon dioxide, which escapes with the products of 
combustion from the flame. The boiling of the bath thus plays a very 
important part in the process. When the slag is thrown aside by the bubbles 
of gas, the metal is exposed to the action of the flame, and though this 
exposure is but momentary in each instance, the large number of such 
exposures result in the formation of a considerable quantity of ferrous oxide 
in this way. But the greatest benefits are derived from the agitation of 
the bath. It is easily seen how this agitation must result in a mixing of 
the slag and metal, thus increasing the area of the reacting surfaces, w’hile 
the stirring effect on the metal itself should not be overlooked. Thus, the 
metal lying near the bottom, which is the coldest and most impure, is 
brought upward to be heated and exposed to the oxidizing influences, so 
that both the temperature and composition of the bath are kept more uniform 
than they could otherwise be maintained. 

Effect of Carbon Elimination on Slag Composition: In conclusion, 
it should be pointed out that the effect of the carbon elimination upon the 
slag is to reduce its content of iron oxides. By proper regulation of the 
conditions this reduction of the oxides in the slag may be brought down to 
the point where the total iron content of the slag will be about 10% of its 
weight, of which iron about 7/l0, or 70%, will be in the ferrous condition. 
The advantages of adding ore to the charge, as may now be readily seen, 
are to increase the speed of the purification and to decrease the waste 
of metal, which is more expensive than ore. 

The Order of Elimination of the elements just reviewed, with the 
exception of sulphur, is the same as the order in which they have been 
discussed, namely, silicon and manganese, phosphorus, and lastly carbon. 
Some reasons why the first three elements are eliminated in this order 
have been mentioned under their respective headings, but nothing has been 




240 


OPEN HEARTH PROCESS 


mentioned that would appear to cause carbon, which is capable, under 
proper conditions, of reducing the compounds of all these elements, to be 
the last element oxidized in the open hearth. The explanation for this 
difference in the chemical properties of carbon is connected with the fact 
that its reducing power increases as the temperature rises. Again, chemical 
action, when it occurs independently of external influences, always takes 
place in the direction that will liberate the most energy, as was pointed 
out in Chapters I and VII. The oxidation of silicon, manganese, and 
phosphorus and the neutralization of the resulting oxides are exothermic 
reactions, whereas the carbon reaction is endothermic. The elimination 
of the four impurities thus takes place in accordance with the amounts of 
heat evolved or absorbed. As an example of these laws, let the elimination 
of silicon and carbon be compared. These reactions with the heat, or 
energy, values involved, are as indicated in the following expressions: 

(1) Si+2 Fe 0= Si 0 2 +2Fe(+64600 cal.) 

—2(65700) +196000=64600 

(2) C+FeO=CO+Fe (—36540 cal.) 

—65700+29160=—36540 

Reaction (1) shows that in the oxidation of one gram of silicon approxi¬ 
mately 2307 cals. (64,600=28=2,307) of heat are evolved, while in the 
oxidation of one gram carbon, as shown by reaction (2) 3,045 cal. of heat are 
absorbed. If now the reduction of silica and carbon monoxide by carbon 
and silicon, respectively, be compared as in reaction (3) and (4), it will 
be seen that, whereas carbon absorbs heat in reducing silica, silicon reducing 
CO, liberates heat. (3) Si0 2 +C=2 CO+Si(—137640 cal.) (4) 2 CO+Si= 

—196000 +2x29160 —2x29160 

SiO2+C(+137640 cal.) It is evident, then, that the oxidation of the carbon 
+196000 

cannot be complete until the silicon has been eliminated. At high tem¬ 
peratures, such as may prevail in parts of the blast furnace or in the electric 
furnace, for example, the heat absorbed in reaction (3) is supplied from 
external sources, which addition of energy causes the carbon to act as a 
reducing agent toward the silica. What has been said with respect to 
silicon also holds true in the case of manganese and phosphorus. In the 
basic open hearth the temperature rises gradually, so that carbon has no 
opportunity to act as a reducing agent toward oxides of these elements. 

Factors Opposing this Order of Elimination: What has been 
written above should not be taken to mean that each element is completely 
and successively eliminated in the order mentioned, for there are other 
laws, such as the law of mass action, for example, that operate to bring 
about the elimination of these elements simultaneously. The oxidation of 
the carbon, for example, evidently begins shortly after the hot metal has 






CHEMISTRY OF THE PROCESS 


241 


been added to the charge, and certainly before the manganese and phos¬ 
phorus have been entirely disposed of. What is implied is that the elimi¬ 
nation of each element in the order named is successively in the ascendency 
until eventually only the carbon, in part, remains to be oxidized. When 
this element has been practically all removed, the bath of metal no longer 
contains reducing agents and is subject to over-oxidation by absorption of 
ferrous oxide, FeO, up to the point of saturation in equilibrium with the 
slag. This fact explains why it is undesirable to make ore additions to 
the slag just previous to tapping, and also why the heat, unless deoxidizing 
agents are added to the bath, should not be held in the furnace for more than a 
few minutes after the carbon content has been lowered to .10%, which figure 
is within about .03% of the minimum carbon content for this process. 


Resume: All that should now be required in order that the chemistry 
of this process may be fixed clearly in mind, is a rapid review of the subject 
matter included under th,e heading of Operation of the Furnace, which will 
now appear in a new light. To begin this review, picture a furnace in the 
course of operation which has received its charge of solid materials for, 
say, a Monell heat. The first effect on this charge will be an increase of 
temperature. The limestone, ore and the lining of the furnace all being 
basic in character, will remain inactive at first, and continue so until they 
will have absorbed sufficient heat to raise their temperature to the point 
where decomposition begins. For limestone this temperature is about 
850° C., while the ore will not give up its oxygen until its temperature is 
near the fusion point, about 1400° C., unless it comes in contact with reducing 
agents. The absorption of heat by the ore and stone is hindered by the 
scrap charged upon them. This material, being a good conductor of heat 
and exposed to the flame, absorbs heat very rapidly, and as soon as the 
temperature rises above the thermo-critical range, oxidation of the iron 
begins, this giving rise to the formation of scale. The melting point of 
this scale is so near that of the metal, that it may remain on the surface 
until the metal itself begins to melt. It is understood, of course, that the 
impurities contained in the scrap will suffer oxidation with the iron. These 
fluids will trickle down over the colder material beneath and will eventually 
reach the ore on the bottom of the furnace. Here, together with additional 
oxide derived from the ore and some silica, lime, etc., collected from various 
sources, this molten scale will go to make up the first slag. This slag, poor 
in silica, but exceedingly rich in iron oxides, especially ferrous oxide, and 
containing some lime also, is well constituted for the work it has to do; 
and with the addition of the hot metal, the purification may begin at once. 
Thus, the silicon, manganese and phosphorus will have been practically 
eliminated from the metal within two hours after the molten metal is 
charged. The extent and character of the purification of the metal at 
the time of the run off with the resulting change in the composition of 
the slag are indicated in the following table of analyses. 




242 


THE OPEN HEARTH PROCESS 


Table 34. Analyses of Hot Metal and Slag Before Charging and at 

Time of First Run=off. 


ANALYSIS OF METAL. 
Per cent, of 


Heat 

No. 


C 

Mn 

P 

S 

Si 

1 

Pig Iron Before 
Charging. 

3.85 

1.55 

.198 

.035 

1.04 

1 

At Time of Run Off.. 

2.39 

.05 

.022 

.040 

.04 

2 

44 44 <4 (4 44 

2.41 

.02 

.053 

.060 

.... 

3 

44 44 44 44 44 

2.45 

.02 

.068 

.049 

.... 

4 

44 44 44 44 *4 

2.80 

.01 

.015 

.043 

.... 

5 

Briquettes Instead of 
Ore Used. 

3.74 

.01 

.043 

.037 

.... 


PARTIAL ANALYSIS OF SLAG. 
Per cent, of 


Si0 2 

FeO 

Fe 2 03 

MnO 

CaO 

MgO 

P 2 0s 

S0 3 

S 



not 







4.72 

66.67 

det’md 

1.30 

18.00 

2.00 

.78 



19.19 

32.86 

5.22 

12.97 

18.38 

6.11 

1.11 



25.18 

17.39 

4.07 

13.16 

17.88 

12.18 


.090 

.029 

23.68 

26.33 

7.10 

13.54 

12.22 

10.14 


.090 

.027 

15.74 

45.16 

7.50 

6.19 

11.34 

5.23 


.165 

.037 

19.30 

42.59 

5.91 

6.84 

12.41 

3.84 


.182 

.063 


From this point the reader should be able to continue this review 
through the oxidation of the carbon unaided, and in doing so, he will have 
fixed in mind the chemistry of the process much more firmly than if he 
but read the inadequately expressed thoughts of another. As a further aid, 
what is said in Chapter V concerning final open hearth slags should be 
referred to. 








































ELECTRIC PROCESS 


243 


CHAPTER IX. 

MANUFACTURE OF STEEL IN ELECTRIC FURNACES. 

SECTION I. 

INTRODUCTORY. 

The Plan of Study: To understand the process of manufacturing 
steel by means of the electric furnace requires some knowledge of electrical 
phenomena. To the question as to what electricity is, no very satisfactory 
definition can be given. The modern idea is, that it is the fundamental 
of which all matter is composed, because there is evidence to indicate that 
electrons are but corpuscles of negative electricity, which, together with 
nuclei of positive electricity, go to form atoms. That it is either a form 
of energy or an agent for transmitting energy is evident, and the various 
phenomena attending it may be due to the production of strained conditions 
in the Ether, somewhat similar to the effect of heat upon water in the 
generation of steam. However, the question is of no importance except to 
distinguish the thing from the phenomena produced by it, which are of 
great importance. To those who have not been able to devote much time 
or study to the subject, these phenomena appear as deep mysteries and are 
difficult to understand. This study may, therefore, be appropriately intro¬ 
duced by a brief explanation, presented in as simple a manner as possible, 
of such of the phenomena and laws of electricity as apply to the subject 
of steel manufacture by this method. To be of the greatest help to those 
unfamiliar with electricity, it is necessary to begin with the fundamentals 
and build up such a structure as the limits of space and time will permit. 

Force, Work, Energy and Potential: In the industrial world the 
fundamental or prime factor is work. It is defined as the operation of 
overcoming resistance through space, or as the production of effects upon 
bodies. That which is the immediate cause of these effects is force, which 
is more accurately defined as that which causes, or tends to cause, a change 
in the motion of a body, in either velocity or direction. Thus, a column 
may exert a powerful force in supporting part of a building, because it 
tends to change the direction of motion the overburden would have if free 
to fall; but it does no work, because no effect is produced. Force is measured 
by the product of the mass of the body it acts upon and the acceleration 
(rate of change of motion) it produces. In the centimeter-gram-second 
(C. G. S.) system the absolute unit of measurement is the dyne, which 
is the force required to produce an acceleration of one centimeter per. sec. 
per. sec. in a mass of one gram. On the foot-pound-second (F. P. S.) system, 
the unit is the pound, which is the force exerted by gravity on a definite 




244 


ELECTRIC PROCESS 


mass of matter. A similar unit on the centimeter-gram-second system is 
the kilogram, which is the force exerted by gravity on a mass of one kilogram. 
That which imparts to a body the ability to do work is energy. Both are, 
therefore, measured by the same unit. In the foot-pound-second 
system this unit is the foot-pound, or the work done by a force of one 
pound acting through a distance of one foot. In the centimeter-gram-second 
system a large unit is called the kilogram-meter, while a small unit, one dyne 
acting through a distance of one centimeter,is called the erg. The joule,equal 
to 10,000,000 ergs, is a more practical unit. Thus, if a weight of 10 lbs. is 
lifted against gravity to a distance of 5 ft., 50 foot-pounds of work has been 
done on that body, and 50 foot-pounds of energy was expended, and the 
same amount of energy is stored up in the body raised in the form of 
potential energy, which imparts to this body the ability to do work. In 
practice the body lifted would be said to have its potential raised, or a 
difference in potential has been effected between this position of the body 
and (the same body in) its former position. 

Power: It will be noticed that work is independent of time. The 
time rate of doing work is called power. In the foot-pound-second system 
the unit is the horse power, (h. p.), which equals 33,000 foot-pounds in one 
minute or 550 foot-pounds in one second. It is based on experiments in which 
it was found that the work an average draft horse can perform continually 
without over-exertion is equivalent to lifting a weight of 150 pounds vertically 
while travelling at the rate of 2.5 miles per hour. In the centimeter-gram- 
second system the unit is the watt, which is that power that will do one 
joule of work in one second. The large unit equals 1000 watts and is 
called kilowatt. This unit is employed in electrical work. 1 kilowatt= 
1.34 h. p., or 1 h. p.,=746 watts=.746 kilowatts. Since energy is conserved, 
power can be supplied only by creating a difference in potential. 

Transmission of Energy: In the mechanical world it is often desir¬ 
able, for economical reasons, to create this potential difference at some 
central point, known as the power station, from which the power may be 
distributed by proper means to various other points and applied as required. 
For the transmission of energy there are four agencies, namely, gases, such 
as steam; liquids, such as water; electricity; and the Ether. In certain 
respects the characteristics exhibited by any one of these agencies in use 
is similar to each of the others. In the first case the difference in potential 
is maintained by making use of the potential, or chemical energy, of fuels 
to generate steam, which may be conducted through pipes to impart motion 
to engines and do work upon matter, or to give up its energy as heat. 
Similarly, water may be made to transmit energy by causing it to flow 
through pipes from high levels to lower ones. Somewhat analogous to the 
flow of the water, is the passage of the electric current along a wire. 
In each case means must be taken to maintain the flow by keeping up a 
difference in potential. In the case of water, a pump could be inserted in 
a circuit for returning the water to the higher level as rapidly as it flows 




ELECTRICAL UNITS 


245 


downward. In practice a pump would be impracticable, but the sun 
accomplishes the same thing by vaporizing water so that it rises into the 
atmosphere to fall again as rain, and thus complete the circuit. In electric 
circuits this difference in potential is maintained by means of the electric 
battery, the static machine, or the dynamo, the last of which will be briefly 
described later. The close similarity between these two cases will be 
readily observed by a study of the following table of analogues, in which 
the water is assumed to be flowing through a horizontal pipe at the point 
of examination: 


Table 35. Hydraulic—Electric Analogues. 


Functions of the Currents 

Hydraulic 

Units 

Electromagnetic 

Units 

Hydraulic 

Electric 

Pressure. 

Quantity. 

E. M. F. or 
Voltage. 

Pressure per sq. 
in. or Head in 

feet. 

Pound. 

Volt. 

Coulomb. 

Rate of flow. 

Amperage. 

Pounds per second 

Coulombs per sec. 

Friction. 

Resistance to con- 

Loss in Head, 

or Amperes. 


duction.. 

No unit. 

Ohm. 

W ork. 

Electrical Energy 
Wattage. 

Foot-pounds. 

Joule. 

Rate of Work. 

Horse-power or 
watt. 

Watt or 

Volt—Ampere. 


One important point of difference between the transmission of water 
and electric current is evident; namely, that whereas water passes through 
a hollow tube, electrifications pass along solid bodies, usually wires. It 
is also common knowledge that electrifications will pass along some sub¬ 
stances very easily and only with difficulty, or not at all, along others. 
No substance is so good a conductor as not to offer some resistance to the 
transfer. Substances that offer little resistance are called conductors; 
those in which the resistance is great, non-conductors or insulators. In 
the following table, the substances named are arranged in the order of 
their conductivities: 


Table 36. 
Conductors 

Metals 

Graphite 

Acids 


Relative Conductivity of Various Substances. 


Salt water 
Linen 
Cotton 
Dry wood 
Paper 


Silk 

India rubber 
Porcelain 
Air 
Glass 


Sealing-wax 

Rubber 

Vulcanite 

Insulators 




































246 


ELECTRIC PROCESS 


Electromotive Force (E. M. F.): While a definition of the various 
electrical units at this time would be out of place, occasion should be made 
to explain electrical pressures. Just as hydraulic pressure might be called 
water-moving force, so pressure produced electrically is called electromo¬ 
tive force (e. m. f.). As indicated above, the unit of measurement for 
electromotive force is the volt, which is also the unit for measuring difference 
in potential. In practice electromotive force and difference in potential 
are different things. Electromotive force refers to the total electrical 
pressure existing in a circuit, whereas difference in potential is merely the 
difference in electrical pressure between two points on the circuit. 

SECTION II. 

THE DEVELOPMENT OF ELECTROMOTIVE FORCES-OR 

“GENERATION OF CURRENT. ” 1 

Methods for Setting up Electric Currents: As already indicated the 
difference in potential between two points, which is necessary to produce an 
electric current, may be created by different methods, of which the most 
common and useful are the following: 1. By friction, as in the electro- 
phorus, or electrostatic machine. 2. By chemical action, such as that 
which takes place in the electric battery, or voltaic cell. 3. By electro¬ 
magnetic induction, as in the dynamo. In all these cases, energy must be 
expended to produce the difference in potential, and the points of different 
potential must be connected by a conductor. Electrostatic machines, while 
they produce a high electromotive force, generate only a small quantity of 
electricity in a given time. Current produced in this way has, therefore, 
a very limited use. In the voltaic cell these conditions of current are 
reversed, the amperage being high and the voltage low. The dynamo can 
be made to give current high in both voltage and amperage. It is, there¬ 
fore, the most useful of all electrical machines, and is the source from 
which the current required by the electric steel furnace is obtained. This 
being the case, a discussion of the principles involved in the working of this 
machine should be both interesting and instructive. To an observer not 
familiar with the subjects of magnetism and electricity, the dynamo appears 
as a machine for changing motion into electrical energy, and, in a way, 
this idea is correct. But the generation of the current is not due to motion 
alone. Other phenomena, known as magnetism and induction, are involved, 
and to understand the generation of the current these must be studied first. 

Magnetism: The attractive force of magnets upon iron is well known. 
Upon investigation, it is foimd that every magnet possesses two poles, 
designated as North and South, N. and S., or + and —,from which lines 
of force issue, and that these lines of force protrude into the space surround¬ 
ing the magnet and extend from pole to pole. In studying the action of one 
magnet upon another, the following laws are observed: 1. Like magnetic 

iFor a fuller study of the generation, transmission and utilization of the elec¬ 
tric current see the standard text books on Physics, also Practical Electricity by 
Terrel Croft and Applied Electricity for Practical Men by Arthur J. Rowland. 
Published by McGraw-Hill Book Company, Inc., New York. 







MAGNETISM 


247 


poles repel one another; while unlike poles attract one another. 2. Lines 
of force having the same direction, i. e., issuing from like poles, repel each 
other; those of opposite direction attract. All these facts are illustrated 
in the accompanying figures, which are diagrams made from photographs 
of actual conditions. 



A 


A 


B 


B 


Fig. 28. Diagrams of Sections through the space surrounding magnets showing lines 
of force between like (A) and unlike (B) poles. Anyone may study these lines of 
force for himself by securing two bar magnets, some iron filings, and a piece of 
paper. The paper is laid upon the magnets and the filings are sprinkled upon it. 
The filings are thus magnetized and arrange themselves in lines or curves corre¬ 
sponding to the lines of force. 

Magnets and Magnetic Substances: Magnets may be natural or 
artificial. Most magnets are artificial and may consist of straight bars or 
rods as shown in the figure, or be curved, as is the case with horse shoe 
magnets. These magnets may be either permanent or temporary. Per¬ 
manent magnets are made of hard steel and retain their magnetism 
indefinitely, whereas temporary magnets are made of soft steel and are 
magnets only so long as they are under the influence of a magnetizing force. 
The space surrounding the magnet through which lines of force pass is 
called the magnetic field, and the number of lines is referred to as the 
magnetic flux. Substances that are attracted by a magnet or are mag¬ 
netized when placed in a magnetic field are called magnetic substances. 
While it can be shown that most substances are affected by magnetism, 
iron, its alloys, and one oxide, Fe 304 , are the only substances available for 
use. These lines of force cannot be insulated, for they pass through all 




















































248 


ELECTRIC PROCESS 


substances, but by the use of a permeable substance, like very soft steel 
or iron, they may be deflected from their course and concentrated in the 
mass of iron as shown in A of Fig. 29. 





Fig. 29. Magnetic Permeability and Induction. 

A. The soft iron washer encloses a space through which there are no lines of force. 
B. Cut in two, the washer becomes a magnet by induction. 


Magnetic Fields and Electric Currents: These magnetic lines of 
force are closely associated with the electric current, for it is easily shown 
that every current bearing conductor is surrounded by a magnetic field, 
the lines of force in which form circles concentric with the conductor. 
These lines of force have a definite direction as in the case of ordinary 
magnets, and this direction bears a fixed relation to the direction of the 
current, as shown in A of Fig. 30. This fact is made use of in producing 
the electromagnet, by coiling the conductor, properly insulated, about a 
core of soft iron, as shown in C of Fig. 30. Such a coil is known as a helix 
or solenoid, and has poles similar to magnets. The various relations 
between flow of current, lines of force, and poles of the helix are shown 
in the figure. The wide application of these facts cannot be discussed here, 
except in so far as they have to do with the development of an electromotive 
force, or, as this is more commonly referred to, the generation of the electric 
current. In connection with the generation of currents, this question might 
arise: If a current produces a magnetic field about a conductor, will the 
production of a magnetic field about a conductor result in a current? This 
question is now to be answered by a brief study of electromagnetic induction. 





















































ELECTROMAGNETISM 


249 


Electromagnetic Induction: The easiest way of bringing about such 
a condition as noted in the preceding paragraph is described in the following 
experiment: If a coil of many turns of fine copper wire is connected to a 
delicate galvanometer and one end of a bar magnet is thrust into it, the 
galvanometer needle will be deflected, showing that a current is set up in 



Fig. 30. Magnetic Fields About Current Bearing Conductors. 

A. Lines of force about a wire carrying a direct current. 

B. Lines of force in the current bearing helix. 

C. The Electro-magnet. The lines of force pass into the soft steel 

bar, which becomes a magnet by induction. 


the coil As long as the magnet remains stationary, no current will pass. 
Upon suddenly withdrawing the magnet, however, a current will again pass, 
but the direction of this second current is opposite to that of the first. If 
these operations be repeated with the other pole of the magnet, similar 
currents will be induced, but in directions opposite to those obtained when 
the first pole is used. Instead of moving the magnet, the coil can be moved 
with a like result, and in place of the magnet a solenoid can be substituted. 
In the last case it may not be necessary to move either the solenoid or the 







































250 


ELECTRIC PROCESS 


coil, as current can be set up in the coil by breaking the circuit or other¬ 
wise interrupting the current in the solenoid. From these facts it would seem 
that the sole cause of the current is the change in magnetic flux. Further 
study of these phenomena reveals the fact that the current induced is affect¬ 
ed by the speed with which the magnet may be inserted and withdrawn, and 
the number of wires in the coil. In the case of the solenoid a third factor 
is introduced, as the current carried by the solenoid itself affects the 
induced current. Furthermore, no current is set up in the coil unless the 
motion is such that its wires cut the lines of force produced by the exciting 
elements: no current is generated if the conductor moves along the lines 
of force. All these facts are summed up in the following laws: 

Laws of Electromagnetic Induction: 1. Any change in the number 
of lines of force passing through a closed conducting circuit induces a current 
in that circuit. (2) The direction of the induced current is always such 
that its magnetic field opposes the motion which produces it (Lenz’s law). 
(3) The electromotive force of the induced current is directly proportional 
to the rate at which the number of linee of force are increased or decreased, 
or, the rate at which the lines of force are cut. 

The Dynamo: Coming now to the practical application of these 
principles, it is found that, of the many electrical appliances depending 
upon them, the dynamo and the transformer are of chief interest in a study 
of the electric furnace. The dynamo is designed to convert mechanical 
energy into electrical energy. The steam engine, for example, does work 
on a dynamo, and the dynamo produces an electric current. This current 
contains all the energy that was received from the engine except a small 
percentage which was lost in heat and friction. There are three essential 
parts of a dynamo: 1st., the field magnets; 2d., the armature; 3d., the 
collecting brushes. The magnets are used to create a strong magnetic 
field between the two poles, that is, a field in which there are many lines 
of force. 



Fig. 31. Diagram Illustrating Essential Parts and Principle of the Dynamo, 
a. Direction in which loop revolves. b and b'. Direction of current through loop, 
c. Direction of lines of force, d and d'. Directi on of current in external part of the circuit. 
















KINDS OF CURRENT 


251 


Hence, in all large dynamos electromagnets are used. The armature 
consists of coils of wire wrapped around a soft iron core; it is mounted so 
as to rotate in the magnetic field and cut lines of force. The current is 
thus generated in the manner described under induction. The essential 
parts of a dynamo are shown in the diagram of Fig. 31, which illustrates 
the arrangement for a drum wound armature. The north-seeking pole of 
the field magnet is marked N; the south-seeking pole, S. The armature 
is here a single loop of wire. The ends of the loop are connected to rings 
which rest on collecting brushes. When the loop is rotated, it cuts the 
lines of force, causing a current to flow out to the brushes and through the 
external part of the circuit. The direction of this flow bears a fixed 
relation to the lines of force as explained under induction and as shown in 
the figure. In practice the following rule is employed to determine the 
direction of the current in the armature. Extend the thumb, first finger, 
and middle finger of the right hand in such a manner that each will be at 
right angles to the other two. Place the hand in such a position that the 
first finger will point in the direction of the lines of force (N. to S.) and 
the thumb in the direction in which the conductor moves. The middle 
finger will then point in the direction in which the current flows. 


SECTION III. 

KINDS OF CURRENT. 

Alternating Current: The current produced in the dynamo 
armature is not a constant one and travelling in one direction, such as is 
obtained by means of batteries, but is an alternating one, as a further study 
of Fig. 31 will show. Let the coil be rotated as indicated by the curved 
arrow above it. While the side at b is moving downward in front of the 
pole N., the side at b' will be moving upward in front of the pole S. An 
application of the law for direction shows that the currents thus induced 
by the two branches of the coil cutting lines of force will flow in opposite 
directions in relation to each other, but in the same direction from end 
to end around the coil. This current continues as long as b and b' are 
moving in the same direction across the lines of force—that is, during 
one-half of one complete rotation. Then, as the rotation continues, the 
sides of the coil cut the lines in an opposite direction, and the current is 
completely reversed. Each time the coil is turned half way around, the 
direction of the current is changed. Each end of the ceil is attached to 
a ring. The rings are attached to the axis of the coil and rotate with it. 
Brushes slide upon the rings and conduct the current out upon the line of 
the external circuit. The line current is thus changed in direction twice 
during each complete rotation of the coil or armature. Each change in 
direction is called an alternation. Two alternations constitute a cycle— 
that is, a circle or series of changes which will be repeated in the next cycle. 
The time required for one cycle is the period. The number of cycles in 




252 


ELECTRIC PROCESS 


one second is the frequency. The frequency is one-half the number of 
alternations in one second. In modern forms of alternators the frequency 
is seldom more than 60 nor less than 25 cycles per second. To produce 
60 cycles in a second with a . c-d 

machine like that shown in Fig. 31, 
the armature would have to make 
3600 rotations in one minute. To 
avoid such high speed, a number 
of pole pieces are arranged in a 
circle around the armature, making 
what is called a multipolar ma¬ 
chine. These poles are wound so 
that north and south-seeking poles 
alternate in position. A cycle is 
then produced in the circuit by the 
passage of any two adjacent poles. 

If there are ten poles, there are 
five cycles during one rotation of 
the armature. A current of 25 
cycles per second would mean 50 
alternations per second or 3000 per 
minute; on a two pole machine it 
would require 1500 r. p. m.; on a 
10 pole, 300 r. p. m. The latter 
is about as Iowa speed as a machine 
can be operated upon economically. 

These are some of the reasons 
why it is not practical to operate 
alternators on cycles over 60 nor 
under 25. 

Graphic Representation of 
Alternating Current: The surges 
of the current are approximately 
harmonic, hence the electromotive 
force may be represented by the 
sine curve, as shown in Fig. 32. 

This figure shows one complete 
wave or cycle, as taking place in 
second of time, and going from zero 
through a positive maximum and 
back to zero, where it continues to 
a negative maximum to return 
again to zero, thus completing a cycle. The different stages of vibration 
represented in the graph are spoken of as phases. Thus b and b' are in 
the same phase, but b and h' are in opposite phases, etc. 






















KINDS OF CURRENTS 


253 


Direct Currents: While all dynamos produce alternating current in the 
armature, this current may be changed to a direct one by means of a com¬ 
mutator properly connected to the armature. How this is done can be 
understood by a study of the accompanying figure. 


Legend: 

a. a. Armature Loops 



Fig. 33. Diagram Illustrating how Current is Rectified by means of a Commutator 

For reasons to be given later, direct currents are not used in furnaces for refining 

iron and steel. 

Polyphase Currents: In order to increase the efficiency and output 
of alternators, recourse is had to polyphase current. These currents 
are the result of attempts to put to economic use the interpolar space, or 
surface of armature core, which is only partly filled in by conductors in 
single phase machines. In any given machine of this kind, which involves 
certain given mechanical and magnetic losses, approximately only half of this 
space is utilized. This waste of space and consequent inefficiency can be 
removed by utilizing the space devoted to the core of the coil for the winding 
of other coils, and thus form a second armature of an equal number of coils 
overlapping the former and utilizing the same magnetic field. In this 
second armature the phase of the current would be a quarter period, 90 
degrees, ahead or behind that of the first, and so would require four wires to 
carry the currents to and from the generator. The output of the machine, 
however, has been doubled. Further attempts to increase output have 
resulted in electrical engineers going even further and constructing triple 
armatures, in which the phase of the currents generated differ by equal 
intervals of % of a period, or 60 degrees. But this scheme then leads to 
considerable elaboration, if the circuits be totally independent with six 
conductors, and very little advantage could be shown to exist over the 
two-phase with four lines. However, in cases where it is possible to arrange 
that the demand in the different circuits be approximately equal and evenly 
distributed, the three phase system can be worked out to great advantage 
by using only three conductors. By referring to the accompanying diagrams 
(Figs. 34 and 35) it will be seen that, at any moment whatever, the sum of 
the electromotive forces in the three circuits is zero. In other words, the 
electromotive force on one line is always equal to that on the other two, 














254 


ELECTRIC PROCESS 


and opposite in kind. Thus, at any instant one of the three wires is to be 
looked upon as the return wire for the other two. 



Fig. 34. Diagrams Illustrating The Methods of Generating the Three Kinds of 
Alternating Current. 

The Two Schemes of Wiring for Three Phase Current: The coils 
of the three phase current alternator, as well as those of the apparatus 
that is to consume the power, may be connected in two different ways 
with each other as shown in the following diagrams. In these diagrams 
the three phase generator is considered as a compound machine made up 
of three separate machines. In such a machine, the separate units may 








































KINDS OF CURRENTS 


255 


be wired independently as shown in Fig. 35A. Instead of three return wires, 
one common return wire may be employed, as shown by the dotted line R 
in the figure. But it is found that, with balanced loads on each system, R is 
a neutral line, that is, no current flows through it; consequently, it is omitted 
as in the figure. The points m and n are therefore called neutral points. 
The form of this diagram suggests the name for the scheme, which is known 
as the star, or Y, connection. In the other schemes the coils of the dynamo 
are connected in a series, and the power is led off through mains connected 
to points in the connecting lines. Fig. 35B shows diagrams intended to 
illustrate the scheme for this connection. On account of the similarity 
to the Greek letter A, this scheme is known as the delta connection. 
It is also called the V and mesh connections. It will be observed that the 
windings of the delta connection form a closed circuit, and the generator there¬ 
fore appears to be short circuited. However, such is not the case, because, 
owing to the fact that the currents generated by the three windings differ 
in phase by 120°, as shown in Fig. 34C, the resultant of the three voltages 
is at every instant zero, hence no current can flow by way of the short circuit. 
With this plan of connections the load may be balanced or unbalanced as each 
coil or set of windings supplies its own load. 




B. Diagram of Delta (Mesh or V) Connections. 

Fig. 35 Diagrams Illustrating the Two Methods of Winding and Wiring for 
Three-Phase Currents. 

These connections are of importance in understanding how the power 
of 3-phase currents is transmitted. They also affect the voltage employed, 


















256 


ELECTRIC PROCESS 


the relations being as shown in the preceding diagrams. The Duquesne 
furnace, for example, operates on 104 volts with star connections and 180 
volts with the delta. This care in explaining three phase current has been 
taken, because it is the most common kind of current and is used in the 
Heroult furnace, the details of which will be explained later. 


SECTION IV. 

TRANSMISSION OF THE CURRENT. 

Ohm’s Law: With this brief explanation of the generation of the 
current, it will be well to turn next to the problem connected with its trans¬ 
mission. Here, also, it is necessary to begin with Hie simplest essentials. 
The most fundamental idea in this connection can be briefly stated in the 
form of a law, known as Ohm’s law. This law states that the strength 
of current passing along a conductor varies directly as the electromotive 
force, or drop in potential, and inversely as the resistance. This law is 
generally put in the form of a formula, thus: 

E Electromotive Force 

1=— or Current=-;- 

R Resistance 

In place of these letters the units which are used in measuring the quantities 
they represent may be substituted, thus: 

V Volts 

A=— or Amperes= ——— 

O Ohms 


By the use of this formula any one of the three quantities may be found, 
provided the other two are given. It may be applied to an entire circuit 
or to a part of a circuit. 


Resistance of Conductors: Referring now to resistance of conductors, 
it will be recalled that, as previously stated, all conductors offer resistance 
to the passage of the current. This resistance can be calculated by applying 
the following law, which has been developed by many experiments. It is 
stated as follows:—The resistance to the flow of an electric current along 
a given conductor at a given temperature varies directly as the length 
and inversely as the area of its section, and is different for different 


substances. 


As a formula, the law is expressed thus: 


R= 


K1 

d 2 


where R= 


resistance, l=length, d 2 =square of the diameter, which is directly pro¬ 
portioned to the area, or the area itself, and K=specific resistance of the 
substance. In the foot-pound-second system, l=length in feet, and d= 
diameter in mils, or thousandths of an inch. A circular mil is the area 
of a circle one mil in diameter. So if the diameter of a wire is expressed 








TRANSMISSION OF CURRENT 


257 


in mils, d 2 =the area in circular mils. The circular mil is not to be con¬ 
fused with the square mil which is the area of a square having sides 1/1000 
inch long. The area of a circle in square mils, the diameter of which is 


expressed in mils 


7rd 2 

: ~^T' 


In this connection the following formulas may be 


found of assistance: 


1. sq. mils=cir. mils X0.7854 


2 . 


cir. mils= 


sq. in. 
.0000007854 


In wire, a length of one foot and a diameter of one mil constitutes a mil= 
foot. The specific resistance of any substance is the resistance of one mil- 
foot. In the following table are the specific resistances of a few substances, 
determined for this system, at 60° F. In the metric system, l=meters, 
d 2 =sq. millemeters, and, of course, K has a numerical value different from 
that by the foot-pound-second system, as shown in the table. 


Table 37. Specific Resistance of Various Substances. 

60° F. 0° C. 


Foot-Pound-Second Centimeter-Gram-Second 
(F. P. S.) System (C. G. S.) System 

Silver. 9.53 .017 

Copper. 10.35 .018 

Aluminum. .03 to .05 

Gold. 13.34 . 

Zinc. 36.46 .06 

Iron. .10 to.12 

Platinum. 58.00 .12 to.16 

Steel. 63.00 .10 to .25 

Molten Steel. . 1-66 to 2.2 at 1700° C. 

Nickel. -15 

Lead. 127.2 .22 

German Silver. 135.0 .15 to .36 

Mercury. 616.16 .94073 




The Ohm, the unit of resistance, may now be defined. It has been 
established by law to be the resistance offered by a mercury column 
1.063 m. long of 1. sq. mm. cross section, and at the temperature of 0° C. 
Originally, the length of the mercury column was one meter. 


Effect of Temperature on Conductors: In connection with the effect 
of temperature upon conductors, it should be noted that there are two 
classes of substances, known as conductors of the first class and conductors 
of the second class. In conductors of the first class, which includes all 
the metals, the resistance increases with a rise in temperature, hence their 
conductivities decrease. This is shown in the case of steel, which at 15 C. 
























258 


ELECTRIC PROCESS 


has a specific resistance of only .10 to .12, whereas at 1700° the specific 
resistance of the molten metal is about 1.66. In the case of carbon and 
conductors of the second class, these relations are reversed, so that they 
become better and better conductors as their temperatures rise. As all 
the refractory materials that go into the construction of furnaces belong 
to this class, this matter must be carefully considered in building electric 
furnaces. 

• 

Resistance in Series and Parallel. In the preceding paragraph, only 
single substances were considered in the circuit. In the actual distribution 
and use of power, it is generally necessary to divide circuits, in which 
divisions different materials or machines will also make up a part of the 
circuit. This division and connections can be made in two ways, namely, 
series and parallel, as shown in the following diagram illustrating two 
methods of light wiring. 



B. Parallel 

Fig. 36. Diagram Illustrating Different Methods of Wiring. 


In Fig. 36 A, the resistance of the line is r and of each of the lamps it 
is r', then the whole resistance, R, is the sum of these four, or 

R=r+r'+r"+r'" or R=r+3r'. 

Resistance of conductors connected in parallel is not found so simply. 
It is deducted from the law of conductivities, which states that the conductiv¬ 
ity of a combination of conductors is equal to the sum of the conductivities 
of the conductors singly. Now, it is self evident that the conductivity is 

represented by — The resistance in the parallel connections above would 
R 

then be found by solving the following: 

i r i_ ^ i 

r— r + r / + r // + ~ 


This matter is of importance in dealing with electric furnaces, as shown 






















TRANSMISSION OF THE CURRENT 


259 


in the following schematic diagram of the wiring of Heroult and Girod 
furnaces, which marks the chief difference between these two furnaces. 


Fig. 37. 



Wiring Diagrams for Heroult and Girod Electric Steel Furnaces. 


These diagrams show the Heroult furnace, on the left, to be connected 
in series and the Girod in parallel. 


Currents Through Divided Circuits: If the different parts of parallel 
connected conductors have equal resistance, then equal currents will flow 
through these parts, as is evident from Ohm’s law, thus, 




As the current is always delivered at a constant voltage, E is the same 
in both cases; hence, if R=R', 1=1'. If the resistances are not the same, 
then I would not equal I'. The current flowing in each conductor, however, 
can be found from the following law: Currents which flow parallel to each 
other vary inversely as the resistance of the parallel connected conductors. 


Self=induction, Impedance, Power Factor: In dealing with alter¬ 
nating currents, Ohm’s law does not hold, for the alternations cause self=* 
inductance in the conductor, that is, they generate currents opposite in 
direction, or kind, to that of the main current; and this inductance also 
offers resistance to the current in addition to that offered by the conductor. 
The sum of these two forces opposing the passage of the current is called 
impedance. If impedance be substituted for resistance, then Ohm’s law 
holds for alternating currents, also. Again, any self-induction in the circuit 
causes a difference in the phase between the electromotive force (voltage) 
and the current (amperage), so that the latter either forges ahead of or 
lags behind the former, and the two do not reach their maxima and 
minima together. Consequently, their product at these points, which 
represents the energy available for consumption, is less than the total 
energy supplied. The ratio, expressed in per cent., between the useful 
voltage, or that which is required to overcome the resistance of the con¬ 
ductors and to produce the heat or do any other work desired, and the 
actual voltage required is called the power factor. 


Heat Developed in Conductors: Since all conductors offer resistance 
to the flow of the current, work is done in overcoming this resistance. In 
doing this work part of the electrical energy is converted into heat energy, 
just as work is done and heat developed in overcoming friction. This heat 























260 


ELECTRIC PROCESS 


can be calculated by means of Joule’s law, who foimd from many experiments 
that the heat developed by a current flowing through a conductor is directly 
proportional to the time, to the resistance, and to the square of the current. 
Mathematically stated, this law is H=K I 2 RT, where H=heat, I=current, 
R=resistance, T=time, and K=a constant, which Joule found to be .24. 


E 

Since from Ohm’s law, 1= or E=IR, H=.24 IET calories, when I is 


measured in ampres, E in volts, and T in seconds. The heat thus developed 
is of much importance in the transmission of current, for if the current be 
sufficiently large this heat may raise the temperature enough to burn off 
the insulation, or even to melt the wire. This heating can be overcome 
in two ways. In the first method, the diameter of the conductors could 
be increased, which would decrease the resistance and increase the carrying 
capacity. That this method has its limits is evident, due to the immense 
weight of wire required in some cases where large current (amperage) is 
required, as is the case with electric furnaces. The second method is 
applicable to alternating current only and illustrates both the adaptability 
of the electric current in general and one advantage of alternating current 
in particular. From Joule’s law it is evident that a current of large voltage 
may be carried on a given wire provided the density, i. e., amperage per 
circular mil or square millimeter be kept low. Since power=amperesX 
* volts, or for alternating current Power=amperes Xvolts X power factor, 
this can be done without reduction in power. But since the furnace requires 
a current of low voltage and high amperage, such a current could not be 
used unless means be taken to change this high-voltage-low-amperage 
current into one of low voltage and high amperage. How this is done can 
be learned from the following description of the transformer. 


The Stationary Transformer: In this instrument the desired trans¬ 
formation is effected by electro-magnetic induction already discussed. Of 
course, then, only those currents which are started and stopped or increased 
and decreased in rapid succession, or those in which the direction of the 
current is changed many times in a second, can be transformed. Such 
current is furnished by the alternator. In structure the transformer con¬ 
sists of two coils of wire side by side with a core composed of many sheets 
of soft iron, or a special silicon steel, packed together. The coils must not 
have any metallic connection with any part of the instrument. The first 
coil, that through which the main current flows, is called the primary. 
The second coil, or that in which the current is induced, is called the 
secondary. 


Kinds of Stationary Transformers: Transformers are of two kinds— 
step-up and step-down. The step-up transformer increases the voltage and 
decreases the amperage. The step-down produces the opposite effect. 
The change depends on the relative number of turns of wire in the primary 
and secondary coils. If, for example, there are 100 turns in the primary 
and 1000 turns in the secondary, the voltage will be increased 10 times 





UTILIZATION OF THE CURRENT 


261 


and the amperage decreased 10 times. This is then a step-up transformer. 
A step-down transformer would reverse these conditions throughout. If 
there are the same number of turns in both coils, the current will not be 
changed except as it may be affected by the transformer efficiency, which 
should be about 98%. 

In regard to the power of the transformed current it will be seen that, 
since, whenever the transformer increases or decreases the voltage, it 
decreases or increases the amperage, the number of watts will be a constant 
quantity. Suppose there is a current of 100 volts and 10 amperes flowing 
through the primary. The power is then 1000 watts. If the transformer 
raises the pressure to 500 volts, the strength of the current will fall to 2 
amperes, but the power of the current is still 1000 watts. A good trans¬ 
former gives out nearly all the energy that is put into it. A small 
percentage, varying from 2% to 5% of the voltage, is converted into heat. 
Usually this heat is prevented from collecting by immersing the coils 
in cylindrical tanks of oil so constructed as to form a circulating system 
through pipes extending externally from the top to the bottom of the 
cylinder. These pipes act like a hot water radiator and serve to keep the 
whole bath and its contents cool. The oil also serves as an insulator.. 
For steel furnaces three phase 25 cycle current is stepped down from 6600' 
volts to 104 on the star connection or 180 on the delta, the latter of which 
is seldom used on molten charges. 

SECTION V. 

THE UTILIZATION OF THE CURRENT IN ELECTRIC FURNACES. 1 

Effects Produced by Electric Current: The heating and magnetic 
effects of electric currents have already been touched upon in connection 
with generators, conductors and transformers. In order to understand 
how the electric current is utilized in electric furnaces it is necessary to 
study these and other effects from a slightly different standpoint; namely, 
their effect upon the metallic charge in the furnace itself. In this con¬ 
nection it may be truly said that there is but one other effect produced 
by the electric current, and this effect is that of bringing about chemical 
action. To the question as to what chemical action is caused by the current 
in the bath of steel, the correct answer is: There is none. As this answer 
is not in accord with chemical effects produced by currents in other 
metallurgical operations, an explanation may be necessary. 

Chemical Action Produced by the Electric Current: As pointed 
out in Chapter I, electrolysis is brought about when electric currents are 
passed through liquids under certain conditions, some well known examples 
being the dissociation of water and the electrolytic separation of aluminum. 
In these instances, however, it will be observed that these chemical changes 
occur only when direct current flows through the electrolytes. If alter- 

iFor a full discussion of electric furnaces See The Electric Furnace by Alfred 
Stansfie’d, Published by McGraw-Hill Book Co., Inc., New York, Electric Furnaces 
in Iron and Steel Industry, by C. H. Yom Baur, published by John Wiley & Sons, 
New York, and Electric Furnaces for Making Iron and Steel by Dorsey A. Lyon 
and Robert M. Keeney Bureau of Mines Bulletin 67. 








262 


ELECTRIC PROCESS 


nating current is used, then the direction of the current is constantly 
changing, and no action, such as noted above, can take place. Furthermore, 
such action would be harmful in carrying out the electro-thermal process 
for steel. While it might be possible with direct current to purify the 
metal by removing the impurities as sulphides, silicides, and phosphides, 
there would be no way of controlling the process so as to prevent the 
reduction of lime, alumina and other oxides, the elements from which 
would then find their way into the metallic bath. This reduction would 
result in a more impure product than the raw material. Designers of 
-electric furnaces for the iron industry will, then, use alternating current 
exclusively and strive in every way to prevent any electrolytic action 
that might result in electrolysis. 

Electrical Units of Measurements: The subject of electrolysis offers 
an opportunity to define another of the primary units used in electrical 
measurements. The ohm has already been defined in studying resistance. 
It now remains to explain how the value of the ampere is fixed. If a current 
be made, by means of suitable electrodes, to pass through a solution of 
silver nitrate, metallic silver will be deposited upon the cathode, or positive 
pole, and the amount of silver thus deposited in a given time will be pro¬ 
portional to the strength of the current. This fact has been made the 
basis for fixing the value of the ampere. The legal definition reads as 
follows:—The ampere is that current which when passed through a 15% 
neutral solution of silver nitrate will deposit .001118 grams of silver in one 
second. The volt is then legally defined as the e. m. f. which will cause 
a current of one ampere to flow through a resistance of one ohm. In fixing 
the value of these units, it was arranged so that the power possessed by a 
current of one ampere under a pressure of one volt is just equal to one watt. 
Hence the power of the current in watts equals the product of the amperage 
and voltage, or W=VXA. The watt=hour is the energy expended in one 
hour when the current is one ampere and the voltage, or pressure, one volt. 
Hence, 60 watts used for one min. or one watt used for 60 min. will give one 
watt hour. A kilo=watt=hour=1000 watt hours. 

The Magnetic Influence of the Current can be of but slight 
importance to the metallurgist. To the designer of induction furnaces they 
are of double importance. On account of a certain motor effect which 
they produce in the molten metal, these forces cause what is known as the 
pinch effect which will often break the circuit. In arc furnaces this motor 
effect is present in the immediate vicinity of the electrodes causing a slight 
motion of the bath. 

Heating the Bath: It is to be imderstood, then, that the only use to 
which the current is applied in the manufacture of steel is for the generation 
of heat. It may be well, therefore, to consider briefly the heating pos¬ 
sibilities of the current in connection with its practical application to this 
purpose. A little thought shows that these possibilities are only three in 
number, and may be called heating by direct resistance, heating by indirect 



METHODS OF HEATING 


263 


resistance, and heating by means of radiation from an arc or arcs. A brief 
discussion of the three methods, which is also made to serve as a means 
of describing the principles of the many makes of furnaces, follows:— 

Heating by Direct Resistance: In the method of heating by direct 
resistance, the necessary heat to keep the bath molten is produced by making 
use of the resistance of the iron itself. In some respects this method would 
appear to offer some advantages. 1. Since heating is effected by the 
passage of the current through the liquid metal, the heat would be uniformly 
distributed throughout the mass. 2. Since the heat generated is pro¬ 
portional to the square of the current, the amount of heat could be regulated 
by changing the resistance of the furnace. 3. Very low voltage currents 
could be used. But the disadvantages outweigh the advantages, as will 
be realized better if they are set along side the advantages, thus: 1. As 
the specific resistance of iron is low, the high temperature required could 
be obtained only by the use of very high amperage, which would require 
exceedingly heavy connections. 2. This draw-back could be overcome by 
increasing the length of the bath and decreasing the cross sectional area;, 
but such an arrangement has been found impracticable on account of the 
large area the bath then covers, which results in great heat losses and 
precludes the easy change of slags and handling of the metal. Hence, all 
early attempts to employ direct resistance for heating proved failures. 
The problem was, however, eventually solved by the invention of the type 
of furnace known as the induction furnace. In these furnaces the bath is 
made to form the closed secondary circuit of a transformer. This secondary 
can then consist of but one coil, as shown in the following diagram 
illustrating the principle of the induction furnace as invented by Colby 
and Ferranti and later improved and adapted to the manufacture of steel 
by Kjellin. 



Fig. 38. Diagram Illustrating Principle of Induction Furnaces. 
Vertical Section of Kjellin Furnace. 


The furnace includes a magnetic circuit, C, formed of the usual 
laminated sheet iron, as in a transformer core. Electric energy is supplied 
to a primary coil, D, while the secondary circuit is formed by the ring of 







































































































264 


ELECTRIC PROCESS 


metal under treatment, contained in the annular cavity, A, forming the 
crucible. Now, when energy, in the form of alternating current is supplied 
to the primary coil, D, it creates a varying magnetic flux in the laminated 
iron core, which in turn induces a current in the closed secondary circuit 
consisting of metal in crucible A. The current density in the secondary 
bears a fixed ratio to the number of turns in the primary coil D, so that 
it is possible by a suitable variation in impressed voltage to subject the 
metal to an extremely heavy current density, the heat being thus produced 
in accordance with Joule’s law simultaneously throughout the entire mass 
of the metallic bath. Because of the limited contact area between slag and 
metal, this type of furnace does not readily lend itself to refining processes, 
if the form shown in the figure be adhered to. However, this form was 
later changed so as to give a central hearth of considerable size. Those 
who have designed furnaces with the object of improving the Kjellin type 
are Frick, Hiorth, Harden, Greene, and others * On account of the low 
specific resistance of iron, it is difficult to reach high temperatures in these 
furnaces. They are, therefore, not well adapted for desulphurizing oper¬ 
ations in which sulphur is removed as sulphide. 

Indirect Resistance Heating offers a second possibility. Instead of 
depending upon the resistance of the bath alone to furnish the heat required, 
some other conductor having a high resistance might be built into the 
furnace in such a way that the heat generated in it would be absorbed by 
the material to be heated. This is the principle employed in many 
laboratory furnaces and in large furnaces for manufacturing carborundum. 
But in applying the method to the manufacture of steel several insurmount¬ 
able difficulties are presented. 1. The resister can not be composed of 
carbon and in contact wdth the metal, on account of the absorption of this 
element by iron. 2. If a suitable resister of another material could be 
found, it could not be placed in the bath, because it would then be in 
parallel with the metal. The only way these difficulties can be overcome 
is by the use of crucibles to contain the molten metal. The impractic¬ 
ability of this method is at once evident, and furnaces of this type 
designed for manufacturing steel have met with no success. 

Arc Heating: The use of the electric arc, which has been mentioned 
as the third possibility for producing h,eat, is the simplest and the most 
practical of all and has found the widest application in the steel industry. 
Some information as to the nature of electric arcs should, therefore, be 
interesting. In beginning, a distinction is to be made between electric 
sparks and electric arcs. While the air is practically a non-conductor, it 
is possible to create such a high difference in potential between two given 
points as to cause a current to jump the gap and establish equilibrium. 
Such conditions occur in electrical storms, and lightning is an example of 
electric sparks. In arcs the current also passes through the air, but it 
will be observed that a much smaller voltage is required to form an arc 



METHODS OF HEATING 


265 


than is needed to cause sparks. The most common example of the arc is 
the arc- lamp. Here the arc is made between two carbon electrodes, but 
in order to strike an arc it is necessary to bring the electrodes into contact, 
after which a gap may be gradually produced and the arc still maintained. 
If the gap becomes too wide, however, the arc will break, hence means of 
regulating the distance between the electrodes must be provided. 
Evidently the air is not the conductor in arcs as in sparks. All these 
phenomena are explained by assuming that some of the electrode material 
is vaporized by the heat of the arc, and that these vapors serve as a con¬ 
ductor of the current. Some idea of the intensity of the heat of this arc, 
which gives the highest temperatures yet attained, is to be had from the 
fact that carbon vaporizes at about 3500° C. 

Methods of Applying the Arc in Arc Furnaces: Furnaces of this 
type, then, depend almost wholly upon this high temperature of the electric 
arc for the heat required by iron and steel baths. The following diagrams 
will illustrate the three possible methods of applying the arc and heating 
the bath. 



Fig. 39. Diagrams Illustrating the Three Ways of Employing the Electric Arc in 

Steel Furnaces. 

In each of these three cases the bath is directly beneath the arc or arcs 
and receives its heat mainly by radiation. All three possibilities are 
practical and have been successfully applied. So these same figures also 
illustrate the principles of the three furnaces of the arc type. 

The Stassano Furnace is represented in principle by Fig. 39A. The 
distinguishing feature of this furnace is that the current does not pass 
through the metal or slag, the heating being accomplished entirely by 
radiation. At first, Stassano built his furnaces so that they could be rocked 
or rotated in order to agitate the bath, but as this feature did not prove 
to be of any advantage, it has now been abandoned. His furnaces are 
now of the tilting type. In practice three phase current is generally used, 
and the three electrodes enter the furnace at an angle through the walls. 
This plan has the effect of placing a limit to the size of the furnace, and 
so few of these furnaces with a capacity greater than two tons have been 
built. From an electrical standpoint, the furnace possesses the important 
advantage of uniform power consumption, thus avoiding harmful fluxuations 
in current. 












































266 


ELECTRIC PROCESS 


Girod Furnaces: The furnace scheme shown in Fig. 39B has been 
developed by several inventors. It was first successfully introduced by 
Girod for the purpose of manufacturing ferro-alloys. As shown in the 
figure the electrodes are inserted in both the top and the bottom of the 
furnace, thereby connecting electrodes, slag and molten metal in series. 
Heat is thus produced in three ways, theoretically at least. By means 
of an arc at the top, the greater portion of the heat is generated. After 
forming the arc, the current, in its downward courses, must pass through 
the layer of slag which, through the heat of the arc above, becomes a con¬ 
ductor of the second class, after which the current is conducted by the 
molten metal to the electrodes at the bottom. In furnaces using a single 
phase current, these bottom electrodes are four or six in number and are 
equally spaced about the periphery of the hearth. In the three-phase 
furnaces there are four upper electrodes, two of which must be in parallel, 
and sixteen bottom electrodes. In all cases the bottom electrodes are made 
of steel and are water cooled. Other designers of this type of furnace are 
Keller, Gronwall, Nathusius, Stobie and Soderburg. 

The Principle of the Heroult Furnace is diagrammatically repre¬ 
sented in Fig. 39C. The practicability of this principle is shown by the 
fact that the Heroult electric steel furnace heads the list of such furnaces 
in use for the manufacture of steel. This popularity of the Heroult furnace 
is due to the fact that the application of this principle gives a furnace of 
the greatest efficiency combined with simplicity of construction and adapt¬ 
ability to many different uses. Details of the construction of this furnace 
will be given later. At present it is desired to explain only the method 
of heating. All the electrodes, as indicated by the figure, are suspended 
from supports over the roof, through which they project to within an inch 
of the surface of the slag. As the electrodes are so far separated from each 
other as to prevent arcs between them, several resistances are introduced 
in series. For example, let the current be considered as passing from A 
to B. Then as the current jumps the gap at the foot of A, it forms an arc 
and passes into the slag, which also has a high resistance. The metal, 
having a much lower resistance, then acts as a conductor for the current 
to the region directly beneath the foot of electrode B, where the current 
must again pass through the layer of slag and form a second arc as it jumps 
the gap between slag and electrodes. It is evident that practically all 
the heat is formed by the arcs above the slag, which acts as a shield to 
the metal and protects it both from the carbon vapors thrown off from 
the foot of the electrode and from the exceedingly high temperature at 
this point. Portions of this heat is next imparted to the metal through 
the slag, where it may be distributed to all parts of the bath by conduction 
and convection. The distribution of the heat is thought to be aided by 
a slight motor effect produced by the current upon the metallic bath. 
Furnaces of this type using single phase and three phase current are in use. 
The only change necessary to be made for three-phase current is the insertion 





METALLURGY 


267 


of a third electrode. In the development of these furnaces Heroult stands 
almost alone, though slight modifications have been introduced by Chaplet 
and Anderson. 

Some General Conclusions: From what has been said, the following 
facts are evident: 1. That the only part the electric current plays in the 
manufacture of steel is in the production of heat. 2. That for producing 
this heat there are really but two methods available, which has resulted 
in two successful types of furnaces, namely, the induction type and the 
arc type. 3. That from a strictly metallurgical point of view no one of 
these types represents any marked advantage over the other, in their 
present high state of development. This statement has no relation to 
claims of the inventors to mechanical and electrical points of excellence in 
their respective apparatus. What advantage electric heating has over 
other methods of heating is now to be discussed. 


SECTION VI. 

GENERAL FEATURES PERTAINING TO THE METALLURGY OF STEEL MADE 

BY ELECTRO-THERMAL PROCESSES. 

Advantages of Electric Heating: To the metallurgist the electric 
method of heating is an ideal one for the following reasons, which are 
characteristic of it: 1. It makes heat available very quickly and at will, 
and gives an unusually high temperature. 2. The heat may be regulated 
very nicely, which fact permits a charge to be brought to any temperature 
desired and to be maintained steadily at that temperature. 3. Being the 
cleanest of heating agents, it exerts no deleterious effect upon the material 
heated by the evolution of harmful gases. 4. It permits oxidizing: 
reducing or neutral operations to be carried on at will. How these 
characteristics of electric heating work to the advantage of the metallurgist 
and permit him to obtain a product of the highest quality from raw 
materials of any grade will be understood from a study of the topics to 
follow. In this connection the chemical possibilities are of first importance. 

Refining Procedure: The first effect of the characteristics noted 
above is to bring the whole operation of refining metal under complete 
control. The electric furnace is to the metallurgist what the casserole and 
crucible are to the chemist. The bath, then, represents a mixture of com¬ 
pounds and elements, any one of which may be removed at will by the 
use of the proper reagents. The condition may be illustrated by assuming 
a furnace is to be charged with the crudest of raw materials, cold pig iron, 
and then showing how each impurity is removed. A study of the practice 
of many plants shows that the following procedure would be carried out: 
After the furnace has received its metallic charge, an oxidizing flux of lime 
and iron ore will be added. A part of this flux may be charged ahead of 
the metal, exactly as in the case of the basic open hearth. After the charge 





268 


ELECTRIC PROCESS 


has been melted down, the furnace will be tilted slightly and the slag which 
has formed will be carefully raked off. This addition of flux and removal 
of slag will be repeated as often as may be necessary. A cleansing flux 
of lime alone will then be added and raked off. During this period the 
temperature should be kept low, because phosphorus is not readily oxidized 
at high temperatures in the presence of carbon. The bath will then be 
covered with a flux consisting of about 5 parts lime, 1 part sand or other 
form of silica, 1 part fluorspar, and }zi part of carbon in some convenient 
form, such as coke, coke carbon, old electrode, etc. The furnace will then 
be tightly closed, and the temperature raised. In the case of induction 
furnaces, it wall be found necessary after about two hours to introduce 
small portions of ferro silicon, silico-aluminum, or silico-spiegel. These 
alloys act energetically as deoxidizers and form a fluid slag which rises 
to the surface. In the Heroult furnace carbon is the only deoxidizer used. 
After the steel shall have been thoroughly deoxidized, any carburizing 
material or alloys will be added to bring the steel to the desired com¬ 
position. When all such material will have been melted, and sufficient 
time will have elapsed to permit them to mix with the bath, the molten 
steel will be poured as a finished ingot product. This process divides 
itself into three distinct periods, namely, an oxidizing period, a reducing 
period, and a finishing period, a combination of conditions impossible of 
attainment in any other process. The action brought about during each 
of these periods, and the reasons for using the reagents employed may now 
be discussed. 

The Oxidizing Period: It is evident that the action of the oxidizing 
flux must result in the removal of silicon, manganese and phosphorus in a 
manner similar to that of the basic process. The important distinction 
between open hearths and electric furnaces should be noted here. It is 
this: All the oxygen introduced into the electric furnace must be in the 
solid form as observed above, and the amount can be easily controlled, 
whereas the air admitted to open hearths furnishes an unlimited amount 
of oxygen that cannot be controlled. Therefore, since these three elements 
are easily oxidized at low temperatures before the carbon, the reaction 
may be stopped and the bath held at almost any carbon content desired. 
With respect to phosphorus, it has been suggested that this element may 
be removed as phosphide by means of some metal, as calcium. While this 
scheme is theoretically possible, it is still impracticable, for it is a difficult 
thing to find a metal that would not alloy with iron in preference to com¬ 
bining with phosphorus, or whose phosphides would not so alloy. Quite 
frequently, traces of phosphorus are found in the reducing slags, but this 
method of eliminating phosphorus, though often attempted, has not been 
made successful beyond the removal of very small amounts and at great 
expense. Hence, the only sure way of removing this element is to oxidize 
it to phosphoric acid, neutralize with lime, and rake off the resulting slag. 
In refining purer materials than pig iron, where the removal of silicon 




METALLURGY 


269 


and manganese would not be required, the oxidizing slag is called the 
dephosphorizing slag. Considerable sulphur is removed during this period 
in the electric furnace, especially where an ore high in manganese is used, 
whereas in the basic furnace, its removal is a very uncertain quantity. 

The Reducing Period: This is the period in which the electric furnace 
exhibits its great superiority over other modes of refining iron. During 
the period, the bath is almost completely deoxidized by means of carbon 
alone, and the removal of sulphur is positive and can be made almost com¬ 
plete. Its entire removal seems to be impracticable, as a content of less 
than .010% is obtained only after prolonged and expensive treatment. 
The flux added is, therefore, called either the desulphurizing or deoxidizing 
flux. 

Oxygen: Oxygen occurs in steel principally as FeO, as has been stated 
in previous chapters, in which its harmful effects were also dwelt upon. 
Its removal may be represented by the following equation in which M 
may represent a great number of suitable elements: 

FeO+M==MO+Fe. 

The deoxidation may be brought about in the induction furnace only 
by means of the special deoxidizers previously noted, whereas in the Heroult 
furnace carbon alone may be employed. -The use of carbon alone has been 
objected to because it was argued that the use of this element would give 
the oxide, CO, which is a gas, and the formation of this gas in the metal 
is objectionable. That steel at high temperature either combines with or 
dissolves this gas is fairly well established, for by experiment it has been 
shown that a given steel has a higher melting point in an atmosphere such 
as nitrogen than it has in an atmosphere of carbon monoxide. There is 
also good reason to believe that this gas is again liberated at certain tem¬ 
peratures on cooling. If this be true, then deoxidizing with carbon may 
give opportunity for formation of blow holes and other defects in the ingots. 
Some metal, then, whose oxide is a solid that will easily come to the surface 
as slag is to be preferred for this purpose. This metal must not be volatile 
at high temperatures and must dissolve or alloy with the iron. The metals 
that best meet these requirements are the ferro-alloys of manganese, silicon, 
vanadium, titanium, and metallic aluminum. For many reasons manganese, 
silicon and aluminum have proved the most satisfactory deoxidizers. How 
the carbon, acting through one or more of these elements, may be used 
to accomplish the deoxidation without injury to the steel is well illustrated 
by the practice at Duquesne, to be described later. 

Removal of Sulphur: According to the statements of authorities 
upon the subject, sulphur may be removed in five ways: (1) As calcium 
sulphide, formed by the action of lime and carbon on ferrous sulphide at 
the high temperature of the arc furnace; (2) As calcium sulphide from 
the reaction of lime, ferrous sulphide, and calcium carbide at the higher 





270 


ELECTRIC PROCESS 


temperatures of the arc furnaces; (3) As calcium sulphide through the 
reaction of lime, ferrous sulphide, and silicon at the lower slag temperatures 
of the induction furnace; (4) As calcium sulphide through the reaction of 
calcium fluoride, ferrous sulphide, and silicon; (5) As iron sulphide from 
the action of ferrous oxide on calcium sulphide. The reactions illustrating 
the removal of sulphur in electric furnaces are as follows: 

(1) FeS+CaO+C=Fe+CaS+CO. Occurs in arc furnaces only. 

(2) 3 FeS+2 CaO+CaC 2 =3 Fe+3 CaS+2 CO. in arc furnaces only. 

(3) 2FeS+2Ca0+Si=2Fe+2CaS+Si02.—Used with induction furnaces. 

(4) 2CaF2+2FeS+Si=2CaS+SiF 4 +2Fe. May occur in either induc¬ 
tion or arc furnaces. 

(5) FeS+CaO =■= CaS+FeO. May occur in arc furnaces. 

An inspection of these reactions shows that certain requirements must 
be met before the elimination of sulphur can be brought about. Thus, 
in all cases a highly basic slag is essential, and in no case can desulphur¬ 
ization be effected before deoxidation of the metal and slag has been accom¬ 
plished. The importance of the presence of elementary carbon or silicon 
is evident, and both these elements tend to react with iron or manganese 
oxides rather than with sulphides and lime. Furthermore, reaction (5) 
is reversible, acting from right to left in the presence of very slight oxidizing 
influences. Because of the relation in concentration maintained between 
oxides in the metal and oxides in the slag, both deoxidation and 
desulphurization of the metal may be brought about by additions 
of carbon to the slag, if the temperature is sufficiently high. In 
arc furnaces this method is employed almost exclusively; but induction 
furnaces, owing to their lower temperatures, require that desulphuri¬ 
zation be effected by the use of silicon as shown in reaction (3) and 
(4), both of which take place at much lower temperatures than (1) and 
(2). In the arc furnace complete deoxidation of metal and slag is 
recognized by the presence of calcium carbide in the slag. 

The Finishing Period: With the dephosphorization and subsequent 
deoxidation of the bath, the contents of the furnace may be brought to a 
neutral or slightly reducing state, when the final additions may be made 
for finishing the steel to specifications. In order to save time it is a common 
practice to make some additions before the desulphurizing period com¬ 
mences, especially if the additions are to be made in large quantities, 
which would chill the bath if added all at one time. As the conditions 
are reducing or neutral, loss of alloying elements is reduced to a minimum, 
and the composition of the steel can be controlled with precision. The 





METALLURGY 


271 


ability to finish the steel in the furnace gives the electric process another 
advantage over any of the older processes, also, as this practice tends to 
produce greater uniformity in the steel. 

Some Comparisons: When deoxidation of the bath is complete the 
contents of the electric furnace represents the nearest approach to perfect 
chemical equilibrium that has yet been attained in other large metal¬ 
lurgical operations. In the converter and the open hearth the metals are 
subjected to the action of air and gas; in the crucible the metal takes up 
carbon and silicon; but in the electric furnace, the action of the metal on 
the basic lining being very slight, there is no exchange of elements 
between metal and slag, if traces of phosphorus be excepted. 1 Of course, 
if the dephosphorizing slag of the oxidizing period has not been completely 
removed before deoxidization begins, some of the phosphorus compounds 
in this slag, as well as some in the new slag, will be reduced. However, 
with careful watching, this gathering-up of phosphorus by the metal may 
be entirely avoided. As to the relative merits of the various types of 
electric furnaces, the results obtained are about equal. However, it is 
evident that arc furnaces are well suited for reducing processes, while 
induction furnaces lend themselves most readily to oxidizing purposes. 

Fluxing Materials used in the electric furnace should be as pure as 
possible and free from injurious amounts of sulphur or phosphorus. The 
lime and fluorspar should not contain more than small amounts of magnesia, 
as it makes the slag less fusible, which fact is of great importance when 
the high basicity of the slags is considered. For recarburizing, a material 
low in volatile matter, phosphorus, and ash should be used. At Duquesne, 
anthracite coal is chiefly employed. 

General Manufacturing Practice: As indicated previously, the 
electric furnace may be used to refine pig iron direct. But as the major 
portion of the refining may be accomplished much more cheaply by one 
of the older methods, direct refining is not economically practiced at present. 
Two courses of procedure, therefore, remain. In the one, cold scrap iron 
and steel of any grade as to quality is remelted and refined to produce 
steel of high quality, while in the other the electric furnace is made part 
of a duplexing process, whereby it is used in conjunction with one of the 
older methods of refining to produce superrefined plain steels or alloy 
steels. This second plan is the one used by the U. S. Steel Corporation. 
At the South Chicago Works, the electric furnace is used in conjunction 
with Bessemer converters and tilting basic open hearth furnaces, and may 
be used in the finishing stage of either a duplex or a triplex process; but 
in either case the steel finished in the electric furnace is taken from the 
open hearth. At Duquesne the duplexing is in connection with basic open 
hearths only, and to furnish a concrete example of the construction and 
workings of the electric furnace this plant will be described. 

Lyon and Keeney, Electric Furnaces for making Iron and Steel. Bureau of 
Mines Bulletin 67, Page 125. 








272 


ELECTRIC PROCESS 


r 



Fig. 40. Heroult Electric Furnace. General View—from pouring side, 





























CONSTRUCTION OF FURNACE 


273 





» 


Fig. 41. Heroult Electric Furnace.—Drawing from Tower Side. 

































































































































































































/ 


274 


ELECTRIC PROCESS 







Fig. 42. Heroult Electric Furnace.—Vertical Section Through Tower and Furnace. 























































































































DUQUESNE PLANT 


275 


SECTION VII. 

THE DUQUESNE PLANT-FEATURES PERTAINING TO ITS CONSTRUCTION. 

Equipment: This plant was completed early in 1917, and is located 
at one end of No. 2 open hearth plant and in the same building. The 
special equipment of the plant may be said to consist of one 20-ton Heroult 
tilting furnace with a transformer station and testing laboratory, three 
charging ladles, three pouring ladles and one traveling over-head crane 
for charging. Other equipment such as teeming cranes, molds, cars, etc. 
are part of the regular equipment of the open hearth plant. The open 
hearth floors are on two levels. The electric furnace, therefore, standing 
in line with the open hearths, is elevated and so constructed that it may 
be charged from the charging floor level, and tapped into the pouring ladle 
on the ground floor thirteen and one half feet below the charging level. 
The transformer station is in a brick building just outside the open hearth 
building, and about eighteen feet from the center of the furnace. Three 
transformers are used, the combined capacity of which is 3500 K. W. 
From the transformers the current is conducted by means of bus bars to 
the corner of the transformer house nearest the pouring side of the furnace. 
Thence it is carried along a large number of heavy copper cables to the 
furnace. Wood bars, tied together like sections of a picket fence, are used 
to insulate the three lines of cables from each other. This arrangement 
furnishes the flexible connections necessary to permit the tilting of the 
furnace. 

Construction of the Furnace Shell: The furnace is circular in form, 
and has an outside diameter of approximately sixteen feet. The shell is 
made of plate steel one inch thick, riveted together. This shell may be 
considered as being made in these three parts: a channelled band for the top, 
which is removable and made up of riveted plates; a side wall which is 
cylindrical in shape; and a bottom, which is shaped somewhat like a hopper. 
The bottom and side walls are riveted together. The shape of the bottom, 
front to back, is made to conform to heavy steel rockers, which rest on two 
heavy castings that serve as tracks. The rockers and tracks are provided 
with teeth, which mesh into each other and thus prevent the furnace from 
creeping. The weight of the furnace is supported by two brick piers upon 
which the tracks, or stationary racks, are bedded. The tops of these piers 
are about five feet above the ground. Attached to the rockers at the back 
of the furnace, are two crank shafts which in turn are connected to two large 
gear wheels, some five feet in diameter. These large wheels are geared to a 
140 h. p. motor, which provides the power for tilting the furnace. 

The Furnace Lining is made up of three layers of different materials. 
Next to the shell, in the bottom and sides, is placed a four and one half 
inch layer of fire brick laid edgewise, and upon this is laid a continuous 
bottom and side wall of magnesite brick. The bottom course is nine 



276 


ELECTRIC PROCESS 



Fig. 43. Heroult Electric Furnace —Perspective Drawing from Top. 













































































































































































































CONSTRUCTION OF FURNACE 


277 


inches thick, while the side wall is thirteen and one half inches in thickness. 
Upon the bottom brick is then sintered a layer, about thirteen inches thick, 
of dead burned magnesite, which is banked on the sides to a safe distance 
above the slag line. 

The Roof is slightly dome-shaped, twelve inches in thickness, and made of 
silica brick set in on end. The first course next the channelled band is 
made up of large skew-back brick. Thus, the roof is made self-supporting. 
As a roof lasts for forty to seventy heats only, two extras are held in 
reserve, ready to be placed in case a roof fails unexpectedly. In the roof, 
three openings are made for the electrodes. Each opening corresponds to 
one vertex of a equilateral triangle, each side of which is about six feet long, 
and the center of which is the center of the roof. When in place, the roof 
sets so that one vertex points toward the vertical guides for the 
electrodes, which are on the side of the furnace next the transformers. 
While in use, the top is bolted to four brackets on the shell to prevent 
the top from slipping when the furnace is tilted. 

Controlling the Electrodes: Through the three openings, noted above, 
the electrodes extend into the furnace for a distance of about four feet. 
In order to make the electrodes adjustable, they are attached to horizontal 
arms that project out over the furnace from heavy vertical rods arranged 
to move up and down within vertical guides. At the top of these rods and 
properly insulated from them, the cables that carry the current from the 
transformer house to the furnace are bolted and welded to bus bars which 
lead to the electrode holders. Thus, the same motion is imparted to both 
the electrode holders and the bus bars. Each of these rods is supported 
and moved by means of a cable attached to its base and leading over a 
small drum geared to a small electric motor. These motors act through 
automatic regulators, which serve to keep the end of the electrode at the 
proper arcing distance from the bath. By reversing a switch on the switch 
board, these motors may be operated independently of the regulator. 
Furthermore, the lifting device is provided with a hand wheel, so as to be 
operated like a common windlass, whereby the electrodes may be regulated 
by hand. 

The Electrode Holders are made in two parts, both of which are in 
the form of a two pronged fork. The upper part is of copper and makes 
the connection between the electrodes and the bus bars, which are securely 
bolted to it. The electrodes are held between the two prongs, and since 
the distance between these prongs is about twenty-four inches, contact 
blocks must be used for electrodes less than twenty-four inches in diam¬ 
eter. A right-and-left screw bolt connects the ends of the two prongs, 
which enables the holder to be opened and closed at will and permits the 
electrode to be securely clamped in place. By this arrangement, electrodes 
of any size up to twenty-four inches diameter may be used. The lower 
part is made of steel and acts as a support for the upper part. These two 
part 3 , carefully insulated from each other, are held together by means of 





278 


ELECTRIC PROCESS 



Fig. 44. Heroult Electric Furnace. General View—Furnace Heady to Charge. 














CONSTRUCTION OF FURNACE 


279 


insulated bolts. Finally, this lower part is fastened to the horizontal arm, 
previously mentioned, by an insulated flange joint. The upper prongs are 
water cooled. 

The Electrodes used at the plant may be of graphite, twelve inches in 
diameter, or of amorphous carbon, twenty-four inches in diameter, and are 
received in sections six feet long. By means of threaded holes in the ends 
of the electrodes and headless screws of the same material to fit, these 
pieces may be joined together so as to give a continuous feed of electrodes 
to the furnace. In this way the great waste of electrodes from unused ends 
is avoided. These threaded holes also serve a useful purpose in removing 
the electrodes and changing them in the holders. As the carbons are 
constantly burning away, this change is frequently necessary. Since the 
electrodes are rather heavy—a six foot length of graphite electrode weighs 
426 lbs.—the use of the crane is made necessary. By means of a linked 
pin of steel, threaded to fit the hole, the electrodes can easily be handled 
with the crane hook. Experience seems to indicate that graphite electrodes 
are best for molten charges but that amorphous electrodes are very well 
suited for use in melting cold charges. A water cooled copper ring encircles 
each electrode at its entrance into the furnace. 

Furnace Openings: Besides the holes in the roof for the three elec¬ 
trodes, the furnace has three openings in the side wall, all located within 
an arc of 180° on the circumference. One is the tapping hole, a small opening 
through which the steel is poured into the steel ladle. This opening is 
provided with a spout, so constructed as to act as a slag skimmer when 
the furnace is tapped. Opposite the tapping hole is the charging door, 
through which the molten metal from the open hearth is charged, while 
half way between these two openings is located a second charging door, 
which can be used only for charging solid materials by hand. Both these 
charging holes are closed with neat fitting brick lined doors, which are 
lifted by means of compressed air cylinders in much the same way as open 
hearth doors. 


SECTION VIII. 

OPERATION OF THE FURNACE. 

Practice at Duquesne Plant: The Duquesne furnace is used to make 
plain steels of any carbon content and many different alloy steels. For all 
the steels made in the furnace the raw material charged is finished basic 
open hearth steel, hence the refining in the electric furnace consists of 
deoxidizing and desulphurizing only. Unless the specifications on the 
basic steel should coincide with those for the electric, which is seldom the 
case, additions are made to the charge either in the transfer ladle or in 




280 


;ELECTRIC PROCESS 


the furnace. No additions of any kind are made in the pouring ladle or at 
the time of tapping, as is the common practice in making open hearth 
steel.' A good example is furnished in the case of carbon. When it is 
necessary to raise the per cent, of this element, as is the case on orders 
calling for a higher per cent, than that of the open hearth heat, the amount 
required above that supplied by other additions is added, in the form of 
anthracite coal, to the steel in the transfer ladle, in the furnace, or a part 
in both. Additions of other elements are, as a rule, added after deoxida^ 
tion of the metal is well advanced or completed. This ability to finish 
the heat in the furnace is a decided advantage in favor of the electric 
process, as a more homogeneous product is thus obtained. 

Charging: Omitting the. mechanical and electrical features, the 
operation of the furnace, in general, is carried out as follows:—Approxi¬ 
mately twenty tons of a suitable open hearth heat is teemed from the 
steel ladle into the charging ladle, for the electric furnace. This charge is 
then conveyed by a dinkey, over a narrow gauge track, to the furnace, 
into which it is poured through a portable spout. During the pouring, a 
test for chemical analysis is taken, and upon the results of this analysis is 
based the approximate amount of carbon and manganese to be added. An 
increase of three to five points in the manganese content of the steel usually 
occurs during the deoxidizing period, and must be allowed for. If a medium 
or high carbon heat is being made from alow carbon open hearth heat, requiring 
the addition of a large amount of carbon, the greater portion of this 
element is added in the form of anthracite coal, which is thrown into the 
furnace as the heat is being charged. This procedure is necessary to 
insure that the coal will be absorbed by the steel. 

Deoxidizing: As soon as the charging has been completed, the elec¬ 
trodes are adjusted, and the current is turned on. Since the charge usually 
freezes over on top, especially in the case of low carbon steels, nothing 
further is done until this solidified layer is completely melted. As soon 
as the bath is in a state of complete fusion, the first slag mixture, consisting 
approximately of four parts lime and one part fluorspar or one part clean 
sand for low carbon heats, is added; for high carbon heats, the mixture 
may contain about one-third part coke dust. Soon after this addition, the 
second sample for chemical analysis is taken to determine the per cent, of 
carbon and manganese in the bath, and while these determinations are 
being made further additions of the first slag mixture takes place. Samples 
of the slag taken at this time are usually brown in color and contain vary¬ 
ing amounts of manganese oxide, which fact shows that the iron oxide in the 
steel is being reduced by the manganese present. A decided brown color 
can be taken to indicate that the deoxidation of the steel is well advanced. 
A second slag mixture composed of suitable proportions of lime, fluor spar, 
sand and coke dust is now added. Soon after the addition of this mixture 
the slag becomes less vitrious, shows a tendency to slake, and begins to 



DUQUESNE PRACTICE 


281 


fade in color. If the heating be continued long enough, with proper addi¬ 
tions of the carbonaceous flux, samples of the slag will slake when cold and 
become gray, or even white, in color. Such behavior of the slag indicates 
that the deoxidation of the bath of metal and slag has been completed. 
This condition is also determined by means of the water test. If at this 
time a small sample of the slag while hot be immersed in a little water, 
the odor of hydrogen sulphide can usually be detected, and, if deoxidation 
is complete, the smell of acetylene gas can also be detected. 

Finishing the Heats: During the deoxidation of the bath the results 
of the second chemical analysis have been reported, and if the per cents, 
of carbon and manganese are satisfactory, any alloys that may be required 
by the order are added as soon as the slag condition will permit. If the 
carbon content should be too low, it is raised to the required point by the 
addition of a proper weight of cold, very low phosphorus pig iron. The 
bath is chilled somewhat by the addition of the alloys, especially if they 
are added in large amounts, and about three-quarters of an hour is required 
to heat the bath up to the tapping temperature. Besides, in order to give 
the alloys time to mix with the steel, no additions are made for thirty 
minutes before tapping except in the case of 50% ferro silicon, which is 
added ten to fifteen minutes before tapping to avoid losses of the 
element. 

Tapping and Teeming: When enough time has elapsed to melt all the 
alloys or other additions, slaking and water tests are made on the slag, and 
if these indicate a satisfactory condition of the slag, the heat is tapped. In 
tapping the heats, care is taken to prevent slag from running into the steel 
ladle with the metal. The special skimmer with which the tapping hole is 
provided for this purpose has already been mentioned. The steel is teemed 
very carefully, being usually box poured. In this method of teeming the 
stream of molten metal from the ladle flows into the middle of a box made 
in three compartments. From the middle compartment the steel overflows 
into the two end ones, which are provided with nozzles. This arrangement 
permits these nozzles to be carefully centered over two ingot moulds before 
the pouring is begun. Special care is taken in preparing the ingot moulds, 
so as to prevent ingot defects due to bad moulds. The steel is allowed 
to stand two hours in the moulds, so as to insure that solidification is 
complete before it is stripped. 

Scrap Heats: Besides the refining of molten open hearth steel, which 
has just been described, the furnace is occasionally used to make steel 
from scrap. When using scrap, two methods may be followed. Thus, 
the charge may consist of cold scrap or be made up of scrap and molten 
steel. When scrap alone is used, it must be small, and the coarser material 
is charged first with the finest on the top. Even then the power fluctuations 
are great, and some difficulty is experienced in melting the scrap. These 




282 


ELECTRIC PROCESS 


difficulties are over-come for the most part by starting the furnace on a 
short charge of molten steel and then adding the scrap to this charge. 
This latter method is the one employed most often at this plant. After 
the melting period the procedure is then the same as that already described 
for molten charges. An examination of the following tables will give a more 
concrete idea of the method of handling the different kinds of steel made 
in the electric furnace. 

Table 38. Showing History of a Heat of Low Carbon PJain Steel 

Made in the Electric Furnace. 

Analysis of molten charge—steel as finished at open hearth: C.=.09%; 
Mn.=.38%; P.=.014%; S=.043%. 

Order: C. .10/.15%; Mn.=.30/.50%; P. under .035%; S. under .040%; 
Si. under .04%. 

Time Additions 

8:10 Charge, 46700 lbs. Test. C.=.06%; Mn.=.33%; P.=.010%; 
S.=.038%. 

8:35 Power on. 

9:35 1st slag mixture. Lime, 500 lbs., fluor spar, 150 lbs. 

9:50 485 lbs. pig iron added. 

10:00 34 second slag mixture, Lime, 750 Lbs., fluor spar, 125 lbs., coke 

dust, 100 lbs; sand, 100 lbs. 

10:05 Sample for chemical analysis. 

10:20 104 lbs. ferro manganese added cold. (Laboratory report shows 

C.=.08%; Mn.=.19%.) 

10:30 Chemical analysis, C.=.10%; Mn.=.32%. 

10:45 50 lbs. Ferro manganese added cold. 

10:50 300 lbs. pig iron added cold. 

10:55 l /2 second slag mixture. 

11:00 34 third slag mixture—Lime, 100 lbs.; fluor spar, 30 lbs.; coke dust, 
75 lbs. 

11:30 third slag mixture. 

11:40 34 third slag mixture. 

11:45 34 third slag mixture. 

12:00 20 lbs. coke dust. 

12:30 30 lbs. coke dust. 

12:35 50 lbs. ferro manganese added cold. 

12:50 Heat tapped. 

Final analysis: C.=.12%; Mn.=.35%; P.=.007%; S.=.035%; 
Si.=.01%. 




DUQUESNE PRACTICE 


283 


Table 39. A Heat of High Carbon Plain Steel. 


Molten charge—Steel as finished at open hearth—C.=.19%; Mn.=.28%; 
P.=.016%; S.=.041%; 

Order: C.==.95/1.05%; Mn.=.20/.35%; P.=under.030%; S.=under.030%; 
Si.=.10/.25%. 


Time Additions 

3:20 150 lbs. Anthracite Coal added to ladle. 

3:30 Charge, 52400 lbs. Test: C — .29%; Mn — .23%; P.=.012%; 

S.=.042%. 

660 lbs. Coal added in furnace as heat is being charged. 

3:35 155 lbs. coal added. 

3:40 Power on. 

5:35 34 first slag mixture. Lime, 1200 lbs.; fluor spar, 200 lbs.; coke dust, 

100 lbs; sand, 100 lbs. 


6:15 Chemical Analysis 


/front door, —C.=.85%; Mn.=.29%. 
/side door, —C.=.85%; Mn.=.28%. 


6:15 34 first slag mixture. 

6:30 l A first slag mixture. 

6:40 34 first slag mixture. 

6:50 34 first slag mixture. 

7:00 34 second slag mixture. Lime, 100 lbs.; fluor spar, 25 lbs.; coke 

dust, 75 lbs. 

7:05 1700 lbs. pig iron. 

7:10 34 second slag mixture. 

7:15 34 second slag mixture. 

7:20 175 lbs. 50% ferro silicon. 

7:40 Power off, and heat tapped. 


Final analysis, C.=.97%; Mn.=.29%; P.=.007%; S.=.016%; Si.=.19%. 





284 


ELECTRIC PROCESS 


Table 40. A Low Carbon Alloy Heat. 


Molten Charge as finished at Open Hearth, C.=.09%; Mn.=.34%; 
P.=.015%; S.=.034%. 

Order: C.=.12/.20%; Mn.=.40/.70%; P.=under .040;% S.=under 
.040%; Si.=under .20%; Cr.=.40/.80%; Ni.=1.00/1.75%. 


Time 

10:55 

11:15 

12:00 

12:30 

12:45 

12:50 

12:55 

1:00 

1:30 

1:45 

1:50 

2:00 


Additions 


Charge, 50800 lbs. Test, C.=.08%; Mn.=.29%; P.=.010%; 
S.=.042%. 


Power on. 


First slag mixture. Lime, 500 lbs.; fluor spar, 150 lbs.; 

Y second slag mixture. Lime, 750 lbs.; fluor spar, 125 lbs.; coke 
dust, 100 lbs; sand, 100 lbs. 


Chemical Analysis 


/front door, C.=.08%; Mn.=.24%. 
/side door, C.=.08%; Mn.=.22%. 


200 lbs. ferro manganese; Mn.=78%. 

446 lbs. ferro chrome; Cr.=70%. 

730 lbs. nickel; Ni.=99%. 

Yz third slag mixture—Lime, 50 lbs.; coke dust, 75 lbs. 
Yl third slag mixture. 

30 lbs. ferro manganese and 60 lbs. 50% ferro silicon. 
Heat tapped. 


Final Analysis, C.=.20%; Mn.=.51%; P.=.009%; S.=.028%; 
Si.=.03%; Cr.=.54%; Ni.=1.28%. 





DUQUESNE PRACTICE 285 


Table 41. A High Carbon Alloy Heat. 

Molten charge—Steel as finished at open hearth—C.=.20%; 
Mn.=.35%; P.=.010%; S.=.035%. 

Order: C.=.95/1.05%; Mn.=.35/.50%; P.=under .030%; S.=under 
.030%; Si.=under .03%; Cr.=1.35/1.65%; V.=over .18%. 


Time 


Additions 


11:48 150 lbs. anthracite coal added in transfer ladle. 

11:50 Charge, 54500 lbs. Test, C.=.07%; Mn.=.34%; P.=.006%; 
S.=.040%. 


12:05 

12:50 

1:20 


Power on. 

% first slag mixture—Lime, 1300 lbs.j fluor spar, 160 lbs; sand, 125 lbs. 

. . , /Front door, C.=.89%; Mn.=.34%. 

Chemical analysis^ ^ c = 90% . Mn .=.35%. 


1:25 slag mixture. 

1:35 ~Vq second slag mixture. Lime, 150 lbs.; coke dust, 150 lbs. 

2:00 1180 lbs. ferro chrome, Cr.=70%. 

2:10 to 2:40 Remainder of second slag mixture added at intervals of ten 
minutes. 

2:55 353 lbs. ferro vanadium. V.===35% 

3:05 60 lbs., 50% ferro silicon. 

3:30 Heat tapped. 


Final analysis, C.=.99%; Mn.=.35%; P.=.006%; S.=.017%; Si.=.07%; 
Cr.=1.44%; V.=.22%. 




286 


ELECTRIC PROCESS 


SECTION IX. 


THE CHEMISTRY OF THE PROCESS. 


Deoxidation of the Bath: The tracing of the chemical changes that 
take place in the process employed at this plant furnishes an interesting 
study. Since the charge is finished open hearth steel containing the usual 
amount of manganese, it is to be expected that this element would play 
a most important part in the deoxidation of the steel. The fact, plainly 
shown by the preceding records, that the manganese is usually several 
points lower in the charging test than in the open hearth steel is proof of 
its deoxidizing action, which would be expected to continue in the furnace. 
The removal of oxygen, then, is represented by the following reaction: 
FeO+Mn=MnO+Fe. The MnO, being less soluble in the molten metal 
than FeO, rises to the surface and becomes a part of the slag. This action 
is identical with that in the ladle in finishing open hearth steel, but the 
result is not the same in the two processes for two reasons: First, for want 
of time, the deoxidation is not completed in the ladle, whereas in the electric 
furnace it is complete. Second, the MnO in the electric furnace comes 
under the reducing action of the carbon contained in the slag mixture and 
is reduced, thus: MnO+C=Mn-f-CO. The carbon monoxide, CO, being a 
gas, becomes a part of the atmosphere of the furnace, and the manganese 
returns to the bath, as is indicated by the fact that the per cent, manganese 
in the steel usually rises after the addition of the carbonaceous flux. 

Desulphurizing the Metal: With the elimination of oxides from the 
slag, the lime, under the influence of the extremely high temperature of 
the arc which prevails under and in the immediate vicinity of the electrodes, 
begins to be reduced by the carbon of the coke dust, with the consequent 
formation of calcium carbide, thus: CaO+3C=CaC2+CO. It is at this 
point that desulphurization takes place. Since manganese sulphide, like 
the oxide, is less soluble in iron than ferrous sulphide, it is probable that 
this element also aids in this process. Whether manganese sulphide or 
ferrous sulphide plays the most important role in the sulphur reactions is 
difficult to decide, but that the removal of the sulphur from the bath takes 
place through the formation of calcium sulphide, which is insoluble in molten 
iron, cannot be doubted. These reactions are two in number and may be 
written thus: 



+3CaS+2 CO 




CHEMISTRY 


287 


With metallic oxides present in the slag, neither of these reactions will take 
place, as the oxide would react with the calcium sulphide, thus: 


CaS+ 


/FeO _/FeS 
\MnO \MnS 


+CaO 


and with calcium carbide according to this reaction: 


CaC 2 + 


/3 FeO _/3 Fe 
\3 MnO \3 Mn 


+CaO+2 CO 


Hence the presence of CaC 2 in the slag is a guarantee that the bath is 
deoxidized. In the water test the presence of considerable quantities of 
CaC 2 in the slag is detected by the odor of acetylene gas, which is generated 
in accordance with the following reactions: CaC 2 -fH 2 0=C 2 H 2 +Ca0. 
These facts are further illustrated by the following analysis of heats and 
slags: Slags AZ No. 3 and AZ No. 5 illustrate an undesirable and a desirable 
slag, respectively. The relatively high iron and manganese content of AZ 
No. 3 indicate incomplete deoxidation, with a low sulphur and calcium 
carbide content resulting. 


Table 42. Analysis of Tests from Electric Furnace Heats. 


Heat Number 

Tests 

Carbon 

% 

Mang. 

% 

Phos. 

% 

Sul. 

% 

Si. 

% 


Primary. 

.16 

.35 

.010 

.036 


AZ No. 1, (O. H. Heat 83023) 

1st Preliminary 

.80 

.35 

.006 

.023 

. . 


2d 

.80 

• . . 

.... 

. . • • 

. . 


Final. 

.82 

.35 

.010 

.020 

.16 


Primary. 

.20 

.44 

.012 

.042 


AZ No. 2, (O. H. Heat 88026) 

Preliminary. . . 

.61 

.43 

.010 

.025 



Final. 

.67 

.60 

.009 

.024 



Charging. 

.18 

.41 

.005 

.024 



No. 1 Electrode 

.20 

.60 

.004 

.020 


AZ No. 3, (O. H. Heat 84598) 

No. 2 

.19 

.60 

.006 

.020 



No. 3 

.21 

.59 

.005 

.020 



Final. 

.22 

.58 

.004 

.021 



Charging. 

.19 

.34 

.010 

.032 



No. 1 Electrode 

.22 

.53 

.007 

.026 


AZ No. 4. (O. H. Heat 101523) 

No. 2 

.22 

.54 

.009 

.023 



No. 3 

.22 

.54 

.009 

.023 



Final. 

.20 

.47 

.006 

.029 



Charging. 

.28 

.36 

.009 

.040 


AZ No. 5, (O. H. Heat 101524) 

No. 1 Electrode 

.34 

.54 

.007 

.017 



No. 2 

.32 

.55 

.006 

.015 



Final. 

.33 

.52 

.007 

.020 











































288 


ELECTRIC PROCESS 


Table 43. Partial Analysis of Final Electric Furnace Slags. 


Heat No.’s 

AZ No. 3 

AZ No. 4 

AZ No. 5 

Silica. 

. . 19.58% 

20.48% 

18.40% 

Iron. 

1.09 

.72 

.32 

Total Lime. 

.. CO.38 

61.82 

61.26 

Magnesia. 

. . 10.32 

8.40 

7.27 

Manganese. 

.62 

.60 

.35 

Sulphur. 

.85 

.80 

1.30 

Calcium carbide .. 

.32 

.19 

.46 

Alumina. 

.. 3.04 

3.61 

5.95 


Difficult Specifications: While the electric furnace affords means of 
making steel to very difficult specifications and with a greater degree of 
accuracy than is possible in other processes, yet it has its limitations. 
The case of sulphur furnishes an example. From what has just been said, 
the importance of carbon in the elimination of both oxygen and sulphur is 
evident. In low carbon steels the lowering of the sulphur content to any 
considerable degree becomes a difficult problem, because, if the flux be made 
highly carbonaceous, a necessary condition, there is danger that the steel 
will absorb carbon from the slag, and thus raise the carbon content of the 
steel above the requirements. In the high carbon steels, the absorption of 
carbon by the steel can be allowed for and presents no difficulty, so a more 
highly carbonaceous flux may be used than with low carbons, and a greater 
removal of sulphur results. As previously indicated, the elimination of 
sulphur may be brought about by the use of silicon, as shown in the following 
reactions: 

X ' {2 MnS+ 2 CaO+Si={ 2 ^+2 C aS+ Si0 2 

2 ' {2 MnS+ 2 CaF *+ Si ={2 M„+ 2 CaS+SiF * 

But while it is claimed that little more than the theoretical amount of 
silicon is required, in actual practice a residue of silicon in the steel is 
unavoidable. Hence, this method could not be employed to produce silicon 
free steel. Similar to the method of desulphurizing with carbon, these 
reactions will take place only after the bath has been completely deoxidized. 
For low carbon steels, then, the limit for sulphur should be .040%, while for 
high carbons this limit could be reduced to .030%. To guarantee lower 
limits than these would mean increased cost in production out of proportion 
to the benefits to be derived, except in the case of steel that is to be used 
for certain special purposes. Since the phosphorus is removed in the basic 
open hearth, the same range in per cent, of this element as is customary 
to allow in open hearth steel should be allowed in electric steel. As to 
alloying elements, the variation in the composition of the alloys used 
makes it desirable to secure as wide a range as possible in the specifications 
for such elements. 











PROPERTIES OF ELECTRIC STEEL 


289 


SECTION X. 

PROPERTIES AND USES OF ELECTRIC STEEL. 

Properties of Electric Steel: We can deal with this topic in a no 
more fitting way than to quote from impartial investigators. The following 
is taken from a paper by Messrs. Lyon and Keeney of the Bureau of Mines: 
“For many years all high grade steels were manufactured by the crucible 
process, but since the advent of the electric furnace there has been a gradual 
adoption of that furnace for refining steel. For the complete refining of 
the highest grades of steel the use of the electric furnace is now thoroughly 
established. Any products that can be made by the crucible process can 
be made by the electric furnace, and in most cases with cheaper raw 
materials and at a low cost. In the electric furnace complex alloy steels 
can be made with precision. The high temperatures attainable facilitate 
the reactions, and alloys need not be used so largely for the purpose of 
removing gas. Very low carbon steels can be kept fluid at the high tem¬ 
peratures. Steels free from impurities and of great value for electrical 
apparatus can be made. With the electric furnace large castings can be 
made from one furnace, whereas in the crucible process steel from several 
crucibles must be used. For small castings, which require a very high 
grade metal free from slags and oxides, electrically refined steel is especially 
adapted. The electric furnace gives a metal of low or high carbon content 
as desired, hot enough to pour into thin molds, and steel free from slags 
and gases.” 

“There is now a tendency among customers of rail and structural steel 
to require a higher grade steel at an increased price rather than steel of 
acid Bessemer or even of basic open hearth grade at a lower price. With 
the high cost of power that now prevails throughout the steel centers of 
the United States the electric furnace can not compete profitably with either 
the acid Bessemer or the basic open hearth process in manufacturing steel of • 
like grade from pig iron. It is in combination with either of these processes 
that the electric furnace seems destined to be prominent in steel manu¬ 
facture.’ ’ 

“Experiments conducted by the United States Steel Corporation during 
the past four years show that, as compared with the acid Bessemer and 
basic open hearth processes, the electric process has the following advan¬ 
tages: A more complete removal of oxygen; the absence of oxides caused 
by the addition of silicon, manganese, etc;—the production of steel ingots 
of 8 tons weight and smaller that are practically free from segregation; 
reduction of the sulphur content to 0.005 per cent., if desired; reduction 
of the phosphorus content to .005 per cent, as in the basic open hearth 
process, but with complete removal of oxygen.” 



290 


ELECTRIC PROCESS 


“About 5,600 tons of standard electric rails from electric furnace steel 
have been in service in the United States for the past two years (prior to 
1914). These rails have been subjected to all sorts of weather and to 
temperatures as low as—52° F. It seems that rails made by the basic 
electric process can be made softer than by either the acid Bessemer or 
basic open hearth processes and yet show highly satisfactory wearing 
qualities.” 

“No steel rails made by the basic electric process in service in this 
country have been broken. Electric furnace steel of a given tensile strength 
has a slightly greater elongation than basic open hearth steel and is some¬ 
what denser than basic open hearth or acid Bessemer steel.*! 

The results of some comparative tests, made at South Chicago of 
electric furnace steel for plates and basic open hearth steel for plates were 
as follows:— 


Table 44. Comparison of Mechanical Properties of Electric and 

Open Hearth Plate Steel. 


ELECTRIC 

OPEN HEARTH 

Carbon 
Content 
Per Cent. 

Ultimate 
Strength 
per Sq. In. 
Pounds 

Elongation 
on 2 Inches 
Per Cent. 

Carbon 
Content 
Per Cent. 

Ultimate 
Strength 
per Sq. In. 
Pounds 

Elongation 
on 2 Inches 
Per Cent. 

0.08 

59,194 

27.25 

0.08 

51,690 

32.00 

.12 

64,080 

26.05 

.12 

56,510 

29.70 

.16 

69,220 

25.25 

.16 

52,901 

28.61 

.20 

72,853 

22.82 

.20 

58,294 

28.82 

.24 

69,540 

23.12 

.24 

63.560 

26.25 


The results show a 15.5 per cent, increase in ultimate strength and 
11.3% decrease in elongation for electric steel, as compared with open hearth 
plate steel of approximately the same chemical composition.” 


Illinois Steel Company’s Tests on Rails : The Illinois Steel Company 
have conducted a series of experiments from which it was shown that electric 
steel is considerably more ductile at low temperatures than either the open 
hearth or the Bessemer steel. In these tests about 900 pieces of electric, 
open hearth, and Bessemer rails were tested at temperatures ranging from 
70° F. to —50° F., and the results indicated that while all these steels 
showed a marked decrease in resistance to shock as the temperature was 
lowered, the electric steel was relatively more ductile than either of the 
other two. The following table is a summary of the results obtained with 




























USES OF ELECTRIC STEEL 


291 


two open hearth and two electric heats of similar composition chemically, 
as shown by analysis, and may be taken as typical of the general results 
obtained. 


Table 45. Comparison of Tests on Open Hearth and Electric Steel 
Railroad Rails at Different Temperatures. 

Number of Tests, 242. 


Temp 

AVE. No. BLOWS TO 
BREAK RAILS 

DEFLECTION BEFORE 
BREAKING 

ELONGATION IN 12 IN. 

D X' . 













Elec. 

0. H. 

Comparison 

Elec. 

0. H. 

Comparison 

Elec. 

0. H. 

Comparison 




O.H. 

E. Over 



0. H. 

E. Over 



0. H. 

E. Over 




Over 


Inches 

Inches 



Inches 

Inches 






E. 

0. H. 



Over E. 

0. H. 



Over E. 

0. H. 

+60 

3.4S 

3.64 

5% 


2.96 

3.36 

14% 


.808 

.929 

15% 


0 

4.41 

3.82 

15% 

1.41 

1.23 

15% 

.404 

.397 

2% 

—30 

4.55 

2.24 

... 

103% 

1.46 

.58 

.... 

152% 

.420 

.201 

.... 

109% 

—40 

3.31 

2.03 


65% 

.91 

.43 


112% 

.297 

.141 


111% 


Uses of Electric Steel: As to the uses of electric steel, little need be 
said except it may be used with confidence wherever a steel of higher 
quality than that furnished by the open hearth process is desirable. 
So far, the demand for this steel has been in advance of the supply, and 
its application is becoming more and more general. Among those with 
whom it has found favor and by whom it is now being used, are manu¬ 
facturers of automobiles, motorcycles, motor accessories, airplanes, 
machinery, engines, agricultural implements, tools, guns and munitions, 
and by the railroads. The fact that it is being used more and more in 
place of crucible steel is evidence of its superior quality. 

Summary: In order to cover the whole subject of electric steel 
making satisfactorily in so brief a manner, it has been necessary to treat 
the subject from several different view points, which method is likely to 
be confusing, with the result that the reader may have lost sight of some 
important points. In order that these points may receive proper emphasis, 
the following summary of the chapter is appended: 

1. Of the many furnaces in use no one can be said to possess any great 
advantage over any other from a metallurgical point of view, with the 
exception that higher temperatures may be obtained with furnaces of the 
arc type than with the induction type. 

2. The only effect of the electric current is in the production of heat. 



















































292 


SUMMARY 


3. The electric process is the only one in which impurities are not 
added to the steel by the operation. 

4. The electro-thermal process affords the only positive means of 
desulphurizing and deoxidizing steel simultaneously and in the same 
operation. 

5. It permits the addition of all alloying elements while the steel is 
in the furnace. 

6. It provides a way for remelting alloy steel scrap and producing a 
product of high quality without loss. 

7. Steel produced by this process exhibits some unusual wearing 
qualities. 

8. In quality, steel made by this process equals that of the best grades 
of crucible steel. 

9. Much larger quantities of metal may be treated in one operation 
than is possible by the crucible process. 

10. It gives a product that is uniform in quality for any given heat. 

11. Steels refined in the electric furnace are freest from segregation. 

12. Steels made in the electric furnace are free from slag and other 
inclusions. 

13. Electric steel is comparatively more ductile at low temperatures 
than Bessemer or open hearth. 

14. Considering the various methods from an economical point of 
view, the duplexing process in which the electric furnace is used in con¬ 
junction with the basic open hearth combines the greatest capacity and 
efficiency with highest quality of product. 



DUPLEX PROCESS 


293 


CHAPTER X. 

THE DUPLEX AND TRIPLEX PROCESSES. 

SECTION I. 

GENERAL FEATURES OF THE DUPLEX PROCESS. 

What the Duplex Process Is: The term duplex process may be applied 
to a combination of any two processes for manufacturing steel, but it is 
customary among the steel men of this country, at least, to restrict the 
term to mean only a combination of the acid Bessemer and the basic open 
hearth process, in which the latter plays the part of a finishing process. 
Briefly described, the method, as usually carried out, consists, first, of 
blowing molten basic iron in the converter until the silicon, manganese and 
a part of the carbon have been oxidized and then transferring this semi¬ 
finished metal to a basic open hearth furnace, where, through the agencies 
of iron oxide and lime, the phosphorus and the remainder of the carbon 
to be removed are oxidized. The steel is then finished, recarburized and 
deoxidized, according to the usual open hearth practice. This combination 
of processes may be made in other ways, also. One plant, for example, 
in order to produce a very low phosphorus Bessemer steel for a certain 
order, first oxidized the silicon, manganese, and phosphorus in the open 
hearth, and then, by mixing this very high carbon steel with Bessemer 
iron in suitable proportions, succeeded in blowing out the carbon in the 
converter, thus reversing the customary procedure. But as stated in the 
beginning, the duplex process refers to the combination in which the finishing 
operation is conducted in and from a basic open hearth furnace. 

Advantages and Disadvantages of the Process: In the northern 
district of the United States the chief advantages of the process, when 
there is a pressing demand for steel, is that of the increased tonnage which 
it produces in a given time. Thus, while the product is similar in quality 
and of the same grades as basic steel, the time of the open hearth operation 
is shortened by about half; for, whereas one open hearth furnace will turn 
out an average of about fifteen heats in a week of straight running by the 
ordinary way, the same furnace operated as a duplexing unit will produce 
about forty heats in the same period. This shortening of the time of a 
heat saves fuel and tends to prolong the life of the furnace, as does, also, the 
elimination of the silicon in the converter. The process does not require 
the use of scrap, which fact may also be an advantage to some makers. 
Offsetting these advantages, however, are the double conversion cost and 
the decrease in yield, due to the increased oxidation, both of which may be 
very serious drawbacks to the economical production of steel. In dull 




294 


DUPLEX PROCESS 


times, especially, the extra costs of maintaining two separate units may 
more than counter- balance the gain from the increased output. 

Methods of Duplexing: While the details of the process vary widely 
in the different plants, there are two general methods of carrying out the 
duplexing process: Thus, the purification in the converter may be carried 
out to the point where the metal is fully blown and represents a high phos¬ 
phorus steel which may then be mixed with pig iron in the open hearth, 
thus taking the place of steel scrap. In this method either a stationary 
or a tilting furnace can be utilized. But the more common method is the 
one, already mentioned, in which the carbon is only partially eliminated 
in the converter, and the purification then completed by the continuous 
process, which is most conveniently carried out in a Talbot tilting furnace. 
A brief description of these furnaces will simplify the description of the 
process to be given shortly. 

The Talbot Furnace: The object aimed at in the design of these 
furnaces is to permit the removal of any quantity of slag or metal or the 
addition of molten metal, oxidizing agents and flux at any time during the 
working of the charge. They are, therefore, necessarily of the tilting type, 
and are built upon racers and rollers which rest upon the foundation in a 
manner similar, in a general way, to that of the large mixers of recent con¬ 
struction. They are rectangular in shape, and of about the same proportions 
as an ordinary open hearth furnace as to length and width,but they have a much 
greater depth, which increases their capacity for containing molten metal. 
The frame work must be of much stronger construction than that for the 
ordinary open hearth in order to avoid twisting stresses and vibrations 
which would be very harmful to the brick work. Only that section of the 
furnace comprising the hearth, side-walls and roof is made tilting; all the 
ports and flues are stationary, and, together with the checker work, of the 
same construction as for the stationary furnaces. In the best types of con¬ 
struction, these furnaces are so placed and the racers and rollers so formed that 
the center of rotation of the furnace coincides with the center line of the ports, 
so that all its parts always remain in the same relation no matter in what 
direction or to what degree the movable portion of the furnace may be 
tilted. By means of water cooled metal joints, the clearance between the 
movable and stationary parts of the ports is kept very small, so that the 
heating of the furnace may continue even during the tapping of a heat. 
On the pouring side, these furnaces usually have but one opening, a tapping 
hole located above the slag line and provided with a lip or spout for directing 
the stream of molten metal into the steel ladle. As in the case of the 
stationary furnace, doors for introducing the materials into the furnace 
are located in the front side. But unlike the stationary types, the slag 
notches are also placed in front, usually one on each side of the middle 
door, and, of course, at a lower level. Since Talbot’s method is but a 
modification of the basic open hearth process, the furnaces are, as a matter 
of course, provided with basic linings. 





METHOD OF OPERATION 


295 


SECTION II. 

OPERATION OF THE PROCESS. 

An Example of the Duplexing Process: Perhaps the best way to 
describe the duplexing process is through an example. For this purpose 
the method employed by a large steel manufacturing company in the North, 
whose plant represents one of the most recent installations, is selected. 
Their duplexing plant consists of three 20-ton converters and three Talbot 
tilting furnaces, each of which has a capacity of approximately 200 tons. 
While the practice may be varied somewhat to suit conditions, the process 
at this plant is usually carried out about as follows: 

Preparing the Furnace for Charging: The process may be said to 
be continuous for a week, for each week-end the tilting furnace is thoroughly 
drained, the bottom and slag lines are made up, the ports are cleaned and 
repaired, and everything is made ready for the week’s campaign. Of course, 
during the interval of this campaign the front and back wall must be 
attended to and such minor repairs made as are found necessary and there 
is time for. About 6 p. m. Sunday, after the flues have been burned out 
and the gas is once more on the furnace, the work of preparing the slag is 
begun. Four boxes of calcined limestone and three of roll scalp are charged 
and melted down. These amounts are then repeated, and when again molten 
the same amounts are again charged, the total being twelve boxes of lime and 
eight to nine boxes of roll scale. The average weight of a box of the 
lime is 2000 lbs. and of a box of roll scale 3000 lbs. Considerable care 
is given by the melter to the preparation of a good slag, for, as in all open 
hearth work, the success of the process depends on the slag. 

Charging Molten Metal from the Converters for the First Heat: 

At midnight, or shortly afterwards, the metal is ordered from the Bessemer 
department. An average analysis of the mixer metal is as follows: 


Total Carbon. . . 


cent 

Silicon. 

.. 1.55 

U 

Manganese . 

... .67 

U 

Sulphur. 

. . .040 

u 

Phosphorus.. . . 

.365 

u 


The weight of this metal taken for a Bessemer heat is about 40,000 lbs., less 
the weight of the scrap in the converter. Two Bessemer heats, blown in 
different vessels, are poured into a transfer ladle and taken to the tilting 
furnace. When starting up, the first ladle contains metal blown down to 
contain 0.60 per cent, carbon, which is allowed to remain to give a little 
action, or boil, in the furnace. This first ladle is poured into the open hearth 
furnace about midnight. It is followed by a ladle of “soft” metal, 
that is, metal blown down to 0.05% or 0.07% carbon, and then by a 








296 


DUPLEX PROCESS 


“kicker,” or a ladle of high carbon steel. This metal is blown down to 
from 1.5% to 2.0% carbon, and when charged into the open hearth produces 
a vigorous reaction, or boil. The metal and slag are thoroughly mixed 
together by this boil, and during this reaction the phosphorus is largely 
removed from the metal bath and passes into the slag. When the action 
has subsided, another “soft” ladle and a “kicker” are charged. Then, 
if the bath is found to be low in carbon, another kicker ladle is added to it, 
but if high in carbon another “soft” ladle is charged. In this way a bath 
of metal of about 200 tons is produced. The charge is then worked down 
like an ordinary basic open hearth heat until ready for tapping, which is 
usually at about 3:30 a. m. 


Tapping and Recarburizing the First Heat : When the bath is ready 
for tapping, the tap hole is opened and plugged with wet sacking. The 
furnace is then tilted for pouring. Before the sacking is burnt through, 
the slag is up along the back wall so that clean metal free from slag comes 
from the furnace. Only enough slag is drawn off at the end to cover the 
steel in the ladle properly. Some of the steel made in the Talbot furnaces 
is super refined by the electric process, but by far the greater portion is made 
into the ordinary commercial grades which is recarbonized and deoxidized 
in the ladle as for similar grades made in stationary furnaces. 


Preparing the Furnace for the Second Heat: After the first heat 

is tapped, there is a bath of about 100 tons of metal with a carbon content 
of about .15% still in the furnace, covered with the tapping slag. Two 
boxes of lime and two boxes of scale are charged, and two boxes of burnt 
dolomite are used along the slag line, around the doors, etc., as found 
necessary. Then two “soft” ladles of blown metal are charged, and two 
more boxes of lime, which is followed by a “kicker.” During the reaction, 
the furnace is tilted slightly forward and slag is allowed to flow from the 
front of the furnace through the slag spouts, which are under the doors 
directly on each side of the center door. The slag falls into slag cars stand¬ 
ing on the tracks below. Practically all the slag taken from the furnace 
is removed in this way, for, as mentioned before, when tapping a heat only 
enough is taken to cover the metal in the ladle properly. When the reaction 
is over, another box of lime is generally charged, and the bath is worked 
down in the usual way. Very often, another box of lime is spread over 
the slag shortly before tapping, so that five to six boxes of lime are used 
per heat, but as a rule only two boxes of scale are used hete. After the heat 
is tapped, this procedure is repeated, enough slag being taken from the 
front of the furnace at the time of the reaction to maintain a constant and 
proper volume of slag in the furnace. The average time for tapping one 
heat to tapping the next is about three hours. 





TRIPLEX PROCESS 


297 


Closing Down the Furnace for the Week End: About midnight on 
Saturday the furnace is drained. The bath is worked down, so that after 
the heat is tapped there are not more than forty to sixty tons in the 
furnace. Then this residue of metal is tapped and made into soft steel, 
for which there is a constant demand, by making the proper additions of 
ferro-manganese and recarburizer. 

The Slag: At the high temperature at which its removal is effected, 
phosphorus is easily reduced, so in order to oxidize, flux and hold the phos¬ 
phorus in the open hearth slag, it is necessary that tne latter be very basic 
and highly oxidizing, as an analysis shows. The average composition of 
the slag is about as follows: Silica, SiC> 2 , 6.35%; ferrous oxide, FeO, 21.65%; 
ferric oxide, Fe 2 O 3 , 6.90%; manganese, Mn, 1.12%; phosphorus, P, 3.25%; 
alumina, AI 2 O 3 , .97%; lime, CaO, 44.07%; magnesia, MgO, 8.04%. The 
high percentage of iron oxides, which are equivalent to approximately 24.0% 
metallic iron, gives the impression that the process is wasteful of iron, which 
is true, but due to another cause. While the percentage of iron oxide is 
high, it does not exceed that of the run off slags of the open hearth process, 
and the total volume of slag is much less than in the straight open hearth 
process, so that the loss of iron here is perhaps less than in the latter process. 
The chief loss is at the converters, and there can be no doubt but that 
the double conversion loss exceeds the single loss in the straight open hearth 
process. This matter assumes its chief importance as it relates to the 
conservation of the iron ore supply. 


SECTION III. 

COMBINATION PROCESSES IN THE SOUTH. 

The Duplex Process in the South: In the southern district the 
conditions of steel manufacturing are very different from those in the 
North, and many additional reasons for the use of the duplex process there 
are to be found. First, in the South there is no pig iron that is suitable 
for the Bessemer process manufactured there, whereas, in the North, 
Bessemer iron is relatively abundant. Second, there is no low phosphorus 
iron or spiegel commercially available for recarburizing in the southern 
district as there is in the North, and this lack makes it necessary in 
manufacturing high carbon steels in the South to catch the carbon on the 
way down. Third, the phosphorus content of the basic iron in the south¬ 
ern district, which averages about .80%, is very high as compared with 
the phosphorus content of basic iron in the North, the average for which 
is about .25%. In the manufacture of high carbon steel from high phos¬ 
phorus pig iron the duplex process offers exceptional advantages for catch¬ 
ing the carbon high, thus reducing the amount of coal or coke-dust 
required to a minimum and avoiding rephosphorization from the high 
phosphorus slag. Another advantage of the process, when iron with a 




298 ' 


TRIPLEX PROCESS 


high phosphorus content is used, is that it permits the making of a slag 
which contains a high percentage of phosphoric acid and is therefore suit¬ 
able for use in the manufacture of fertilizers. This slag is a valuable by¬ 
product from one of the southern plants. 

The Southern Triplexing Process: In operating the duplex process 
in the South, it has been found that, owing to the high phosphoric acid 
content of the slag, it is difficult to prevent the reduction of some of the 
phosphorus after recarburizing. This rephosphorization of the steel occurs 
mainly in the ladle, particularly in the portion of the metal in direct contact 
with the mass of floating slag, and is most noticeable in the last two or 
three ingots from each ladle of steel teemed. In order to overcome this 
defect and at the same time increase the production of basic slag for phos¬ 
phate fertilizer, one plant has developed a triplex process in which two 
basic open hearth units are required to finish the metal after blowing in 
the converter. Briefly, the process is as follows: After blowing, the metal 
is transferred from the converters to primary basic tilting furnaces where 
it is treated with lime and the other necessary oxides for dephosphorizing 
it. Here the phosphorus content in the metal is reduced to about .07%, 
when it is poured into ladles and transferred by specially constructed, heavy, 
extra-wide-gage trucks to a finishing unit composed of an equal number of 
similar furnaces. In these furnaces the phosphorus content of the metal 
is brought below .04%, when the steel is finished in the ladle by the addition 
of the necessary recarburizer and deoxidizers, and any alloys required by 
the specification. It is said that this process does not reduce the capacity 
of the plant and materially improves the uniformity and quality of the 
steel produced. 




TESTING OF STEEL 


299 


PART II. 

THE SHAPING OF STEEL. 

CHAPTER I. 

THE MECHANICAL PROPERTIES OF STEEL. 

SECTION I. 

SOME GENERAL REMARKS PERTAINING TO THE TESTING OF STEEL. 

The Factors that Affect the Mechanical Properties of Steel: There 
are four factors that may affect the quality and the mechanical properties 
of steel; namely, the method of manufacture, or refinement, the chemical 
composition, the mechanical working it is subjected to, and the heat treat¬ 
ment it receives. The first of these factors is discussed in the first part 
of this book. The others are now to be taken up, and frequent use of the 
terms employed in the mechanical testing of steel will be made in the pages 
to follow. Hence, although in the natural order of manufacturing steel 
physical tests follow the shaping, it seems well to take up this subject now 
in order that the reader may be more familiar with the terms employed 
in connection with these tests, when there is occasion to refer to them. 

The Two Objects in the Testing of Steel: In the early days it was 
the custom to order steel according to use, that is, the purchaser asked 
the steel maker for a certain quantity of steel suitable for a certain purpose, 
and the manufacturer then furnished steel of a kind or grade he considered 
most suitable for the purpose. With the growth of the steel business, this 
custom proved inadequate to the conditions and was superseded by the 
practice of ordering steel to specifications, which appeared to be, and is, 
a much more satisfactory arrangement for all parties concerned. The 
consumer naturally decided that he should know better than anyone else 
what the requirements were, and the manufacturer, in turn, was very glad 
to be relieved of the responsibility he assumed under the old system. Now, 
the only basis upon which the consumer of steel or his engineers originally 
had to work in determining specifications was experience. Thus, providing 
that a certain steel had proved satisfactory for a certain purpose, he desired 
for the new work steel as nearly like the old as possible. With this progress 
came the need for testing. Then as undertakings involving the use of steel 
increased in magnitude, it was discovered that steels made by the same 
methods are subject to considerable variation. Furthermore, in order to 





300 


TESTING OF STEEL 


obtain the requisite amount of steel, it is often necessary to use, for the 
same purpose, steels made in different ways. And again the need for 
testing was felt in order to secure uniformity in the materials. This 
testing developed along two lines, namely, physical and chemical. 

Relative Importance of Physical and Chemical Testing: It is 

evident that, to the consumer of steel, its mechanical properties are of first 
importance, because it is these properties that determine whether or not 
a particular steel is suitable for the purpose he intends it. In all cases, 
then, such as structural steels, in which the material is put in service as 
received from the manufacturer, the customer does well to order his steel 
to physical specifications only. In cases where the steel is to be heat 
treated or is to undergo other treatment in the hands of the customer, 
then it should be ordered to a chemical specification only. Since the method 
of manufacture influences the properties of the metal, the kind of steel, 

| whether Bessemer, basic, acid, or electric, should be and is, usually, specified. 

' But for a great many reasons, for a discussion of which time and space are 
not available, it is unfair to ask the manufacturer to make steel to order 
in which all three factors are specified. Suffice it to say, that in the one 
case the customer should be satisfied to get the kind of steel ordered with 
the required physical properties, irrespective of the means, chemical or 
otherwise, which the manufacturer may have found it necessary to employ 
in order to supply metal with the properties called for. In the other case, 
the purchaser is interested only in obtaining steel properly made and of 
the proper kind and composition, because with such steel the original 
physical properties will be replaced by new ones due to the subsequent 
working or treatments. From the view point of the consumer, then, thfe 
relative importance of the physical and the chemical test depends upon the 
conditions that surround each individual case. But to the manufacturer, 
chemical testing is of prime importance, because it offers a means of control 
whereby he is able to produce the steel with a greater degree of certainty. 
For a description of the methods employed in chemical testing the published 
standard methods of the Steel Corporation are available. 

Nature of Physical Testing: It should at all times be borne in mind 
that the results obtained by any method of physical testing are not absolute, 
but relative. Obviously, the only sure test is actual service, and it 
is just as evident that such tests are impracticable. Therefore, the test 
must be carried out with a small piece of material, the structure and con¬ 
dition of which are likely to be different from that of the section, taken as 
a whole, from which it was cut. A second objectionable feature is found 
in the difficulty of subjecting this piece to the same conditions that it 
would be subjected to in actual service. Attempts have been made to 
analyze these conditions with the idea of classifying the forces steel is 
required to overcome in service, so that in testing it might be subjected 
to the same kinds of forces. With respect to the effect they tend to produce, 





PULLING TEST 


301 


forces have been classified as (1) tensional, or forces tending to put the 
material under tension, that is, pull it asunder; (2) compressional, or forces 
that tend to compress the piece in one or more directions; (3) torsional,or 
forces tending to twist the material; and (4) shearing, or forces that tend 
to cut the material across its section. With respect to the manner in 
which the forces are applied, the following classification has been made; 
1 . Static stresses, which are the result of the gradual application of a 
steady or constant load. 2. Fatigue stresses, such as result from the 
repeated application of a load or loads. 3. Impact stresses, in which the 
metal is subjected to a sudden blow. 4. Dynamic stresses, which are 
repeated impact, or vibratory stresses. 

From these are selected the class of force or stress the steel is likely 
to be required to withstand in service, and the tests will be arranged accord¬ 
ingly. Added to these are a number of miscellaneous tests, such as hardness 
tests and tests to determine relative resistance to wear or penetration. 


SECTION II. 

THE TESTING OF STRUCTURAL AND OTHER SOFT STEELS. 

The Pulling Test: A test that is most commonly applied to steel, 
and one that is always used, and almost to the exclusion of all others, for 
testing structural steels, is that commonly spoken of as the pulling test. 
As the name implies, the chief aim in this test is the determination of the 
tensile strength of the steel, but incidental to the carrying out of the test 
much additional information as to other mechanical properties of the 
sample of steel is obtained. The technical terms employed in testing to 
indicate these properties are tensile strength, elastic limit, elongation, 
reduction of area, and modulus of elasticity. The exact meaning of these 
terms is best explained in connection with a description of the method of 
making the test. 

Procuring the Test Pieces: Except in one or two cases where it is 
desirable to modify the usual procedure, the test piece, or sample, is sheared 
from scrap ends cut from the material as it comes from the rolls. This 
piece is about eighteen inches in length and two inches in width, and, 
except in the case of sheared plates from which both longitudinal and 
transverse pieces are sometimes taken, its long axis is parallel to the 
direction of rolling. As a rule, the test piece is taken from a position not 
too close to the rolled edge, but in the case of bars of small sectional area the 
entire section of the proper length may be taken. The piece is then stamped 
near the ends with the heat number and any other data necessary to 
identify it. 






302 


TESTING OF STEEL 


Preparation of the Test Piece: The working or shearing of the test 
piece puts it in a state of strain and produces a great number of incipient 
cracks on the edges, so that if it were pulled in this condition it would 
fail too easily, and the results of the pulling would not indicate the real value 
of the properties determined. To eliminate these cracks, the edges of the 
piece are milled off as shown in the accompanying sketch, and the milled 



Thickness as Rolled bcale: 4 —1 

Fig. 45. Diagram Showing the Usual Form of the Test Piece Used in Pulling 
Structural Steels. Occasionally the edges are milled parallel for the full length 
of the specimen. 


edges are filed smooth. Then if the piece is a heavy, thick one, or is an 
alloy steel, such as nickel steel, it is allowed to rest for a period, the length 
of which will depend upon the conditions and the kind of steel. This resting 
is necessary to allow the steel to relieve itself of the condition of strain 
which the working has set up in it. This condition seriously affects the 
ductility of the steel, as is shown by the fact that some test pieces, par¬ 
ticularly of alloy steels, show a marked improvement in elongation after 
resting, but with little, if any, change in the tensile strength. In the case 
of soft steels of moderate thickness, the resting period is not so important, 
as the working does not produce severe strains, and such steels recover 
quickly from strains. After the test piece has been machined and filed 
and otherwise made ready for testing, its dimensions are taken. From a 
point estimated to be the middle of the machined portion of the piece, 
two spaces of two inches each are laid off, with a double pointed punch, 
longitudinally along the bar and in both directions from the center punch 
mark, thus making a distance of eight inches between the two punch marks 
that are the farther from the center one. This space fixes the length of bar 
that is later to be the basis for calculating the percentage of elongation. 
Finally, with screw micrometers the width and thickness of the test piece 
are taken and recorded. A careful operator will measure these dimensions 
in three or four places to determine to what extent they are uniform. The 
test piece is then ready to be pulled. 



















PULLING TEST 


303 


Pulling the Test: The testing machine may be likened to a beam 
scale or weighing machine, and if, instead of lying upon the platform of the 
scale, the test piece be thought of as being attached by one of its ends 
under the platform with its other end free for the attachment of some 
device for exerting a vertical pull, the analogy is almost exact. In modern 
machines the pulling device is either an electric motor, attached through 
gears and screws to a gripping device that clamps one end of the test piece, 
or an hydraulic ram connected directly with the clamping device. With 
such an arrangement the amount of the pull is registered in pounds on the 
graduated beam of the machine. This beam is provided with a travelling 
weight, which, by means of a screw and worm drive actuated by hand, 
may be rolled out along the beam as the pull increases, thus keeping the 
beam in the neutral position and registering the amount of the tension at 
all stages of the pull. When the test has been properly marked and 
measured, it is placed in the machine in a vertical position and securely 
clamped in the gripping boxes, or shackles. Then, the pulling device is 
started at low speed, and the weight is cautiously moved out along the beam, 
the operator keeping it in a perfectly horizontal position with the free end 
midway between the upper and lower beam-end stops. The continued 
action of the pulling machine is an indication that the test piece is stretching 
slightly. That such is actually the case could be proved by stopping the 
machine and measuring with delicate instruments the distance between 
the two extreme space marks and comparing this measurement with the 
original length. As the pulling is continued uniformly, the beam weight 
is advanced at a uniform rate, indicating that the piece is obeying the law 
of stress and strain; but a point is soon reached where the beam suddenly 
drops, indicating that, without any increase in the load, there has been a 
sudden increase in the length of the test piece. In testing parlance this 
point is called the elastic limit, the yield point, or the point of permanent 
set. To be accurate, the point reached immediately before this sudden 
stretch, or give, occurs marks the true elastic limit, while the drop of 
the beam marks the yield point. A reading of the weight indicated by 
this position of the beam weight is therefore taken, and the pulling is con¬ 
tinued as before, with the exception that the speed of the pull may be 
increased somewhat. As the beam rises again, it is necessary to advance 
the beam weight much more rapidly than before, which fact indicates a 
more rapid stretching of the test. In a short time another point is reached 
where the beam suddenly drops for the second time, but here, though the 
pulling is continued, the beam will not rise again. A second reading is 
therefore made, and the weight recorded is taken as a measurement of the 
tensile strength of the test piece. Finally, as the machine continues to 
elongate the specimen, the point of rupture is reached, and the piece breaks 
apart. In practice no reading is taken at the breaking point, but if it were, 
it would be necessary to reverse the direction of motion of the beam weight, 




304 


TESTING OF STEEL 


because the breaking load is generally less than the tensile strength. 
The latter, therefore, is usually referred to as the ultimate strength, 
maximum stress, or maximum load. 

Graphic Representation of Tests: The pulling of a test is admirably 
illustrated by means of a graph, which is also a great aid in understanding 
the relations of the various terms employed in designating the points 
described above. The following graph, while not absolutely accurate and 
to scale in some of its parts, will serve to illustrate the scheme for preparing 
graphs and to make clearer the description of the pulling of the test piece. 
The diagram requires no explanation. 



Elongation in tenths of an inch 

Fig. 46. Graph Representing the Pulling of a Structural Steel Test Piece. 

Reasons for the Points of Yield and Maximum Stress: No very 
satisfactory reason for the occurrence of the yield point has yet been 





























































































































PULLING TEST 


305 


advanced. Some think that it is due to some rearrangement of the mole¬ 
cules. Again, grain structure may be the cause. Since steel is made up 
of small grains or crystals, it appears reasonable to suppose that they have 
at the time of their formation assumed a form and an arrangement that is 
most natural, and that they will offer resistance to any force tending to 
change this form or arrangement. This resistance is made up of two forces 
of attraction, namely, one that tends to keep the grains in contact and 
another that tends to preserve the arrangement of the molecules within 
the grain. At the elastic limit this resistance is just balanced by the 
tension, but under any greater tension, deformation of the grains begins, 
and the structure “gives” suddenly, becoming at the same time longer and 
smaller in cross section. Up to the elastic limit the slight stretch may 
be due to a partial rearrangement of the grains. When the tension is 
removed the natural arrangement is restored, with the result that the 
piece immediately assumes its initial form and size. When subjected to 
tension under this limit the body remains in an elastic condition, and the 
deformation it undergoes is called elastic deformation. Above the yield 
point the grains are undergoing deformation, that is, they are in a way 
destroyed, and the piece of metal reacts more like a plastic than an elastic 
body. Therefore the body is said to be undergoing plastic deformation. 
This change in grain form is continuous, and requires an ever-increasing 
force, or stress, to make it so. The condition is strictly analogous to cold 
working, which will be discussed later. Consequently, the piece becomes 
stronger, but at the same time it is becoming longer and correspondingly 
smaller in cross section. Ultimately, as the necking of the piece becomes 
pronoimced, the loss in strength due to the decreased area of the section, 
plus the external stress applied, balances and then exceeds the maximum 
stress that the cold working can develop. From this point, then, the 
external force necessary to balance the forces of attraction between the 
grains becomes less and less as the area continues to decrease rapidly. 
Finally, the maximum deformation of the grains is reached, when, if the 
tension applied externally exceeds the forces of attraction tending to keep 
the grains together at the point of least cross sectional area, the piece is 
fractured at that point. 

Examination of Test After Pulling: After fracture the two parts of 
the test piece are removed from the machine, and the fractured ends are 
fitted together as neatly as possible for the measurements to follow. The 
distance between the extreme punch marks is now measured. The difference 
between this distance and the original space of eight inches gives the elon¬ 
gation for the piece, which is properly recorded. An examination of the 
piece shows that while it has been reduced in section throughout its length, 
the reduction is most pronounced in the region of the fracture, where the 
piece underwent the characteristic deformation known as necking before it 
broke. It is here, as near to the fractured ends as possible, that the width 
and thickness are again measured in order to ascertain the reduction in 




30G 


TESTING OF STEEL 


area. Finally, the fractures are designated as angular, cup-shaped, half 
cup, and irregular. Very little importance can be attached to the form 
of the fracture, but some inspectors believe that the cup shaped fracture 
indicates more nearly perfect uniformity in the material than the other 
forms. 

Calculating the Results of the Test: The results obtained in the 
test are for the given piece only, and, in order that the results from different 
tests may be comparable, they must be calculated to a common basis. 
Tensile strength and elastic limit are always expressed in pounds per square 
inch in the United States, in tons per square inch in England, and kilograms 
per square millemeter in France and other countries using the metric 
system. The elongation is expressed as the percentage of increase on the 
original length of the bar. In the United States this length for structural 
and other low carbon steels is usually eight inches, as formerly stated, but 
other lengths, as ten and twelve inches, ten centimeter, etc., may be used. 
For this reason it is always important that the original length of the bar 
be stated, as the percentage of reduction on two inches, for example, would 
be much greater than that based on eight inches because of the pronounced 
local contraction, or necking, at the point of fracture.. This variation in 
the length of test pieces is made, because the relation between the length 
and the thickness of the test affects the elongation. Hence, in order that 
tests of different thicknesses may be comparable, the ratio between the 
thickness and length is kept constant by varying the length. The ideal 
thickness for a length of eight inches is about three-fourths inch. Over or 
under this thickness, the specification is usually modified either by chang¬ 
ing the length or by making the proper allowance from the elongation as 
determined. The reduction of area is expressed in percentage contraction 
of area of the cross section as compared with the original area of the cross 
section. An example will serve to clear up any doubtful points that may 
not have been made clear in this explanation. 


Table 46. Data on the Pulling Test Represented by the Graph 


of Fig. 46. 

Dimensions of Piece 
Before Pulling After Pulling 

Length.. 8.0 inches 10.20 inches 

Width. 1.41 “ 1.00 “ 

Thickness.860 “ .60 “ 

Area. 1.213 sq. in. .60 sq. in. 


Readings on pulling bar: Elastic limit=44600 lbs.; Ultimate strength= 
74600 lbs. * 








PROPERTIES DETERMINED 


307 


Calculations: 
Elastic Limit 


44,600 

= 36770-lbs. per sq. in. 

l.Zlo 


Ultimate Strength = 


Elongation 


74,600 

1.213 


= 61500- “ “ “ 


10 . 20—8 

---- = 27.5% in 8 inches 


Reduction of Area 


1.213—,60 
1.213 


50.5% 


The Modulus of Elasticity, or Young’s Modulus: The Modulus is 

seldom determined in practical work, as it involves the determination of 

the absolute increase in length of the test bar up to the elastic limit, which 

is a quantity so small as to be very difficult to determine accurately. It 

may be defined as that force, expressed in pounds, tons, or kilograms per 

unit of cross section area, that would stretch a test piece to twice its original 

length, when applied to one end of it and acting in the direction of its length. 

f x L 

It may be found by applying the following formula: M=-where M= 

A x 1 

modulus of elasticity, f=force applied, L=original length, A=original 
sectional area, l=increase in length. For low carbon steel Young’s Modulus 
is about 29,000,000 lbs. 


Relative Importance of the Mechanical Properties as Determined 
by the Pulling Test: From what has been said it is plain that the 
quantities that may be taken as indicative of the strength of the material 
are tensile strength and elastic limit; but while most engineers will insist 
on both tensile strength and elastic limit being given and a few are content 
to get the tensile strength only, it is evident that, in its practical application, 
the elastic limit will determine the working strength of the steel, that is, 
the maximum load a given piece may carry with safety. In the elastic 
range the body stretches and recovers with increase and decrease in the 
load; in the plastic range it cannot recover but continues to elongate 
as long as tensional stresses are applied, and in this condition it is a very 
unsafe material to use. The percentage reduction of area and the percentage 
of elongation are, when considered together, an index of the ductility of 
the metal, for both are required to give an idea of the amount of the 
deformation before rupture. However, engineers are divided in their 












308 


TESTING OF STEEL 


opinions as to the relative importance of the two factors. In a general 
way, it may be stated that the reduction of area is regarded as 
more reliable than elongation, because, as previously explained, the quantity 
denoting the latter is affected by the ratio of the length of the test piece 
to its cross sectional area. In many foreign countries this ratio is always 
specified. 

& 

Bending Tests: On certain classes of material, bending tests are made 
in addition to the pulling test. These tests, simple in character, consist 
merely in bending test pieces similar to those used for pulling, and similarly 
prepared, through certain specified arcs. The bending is usually on cold 
material, but some orders call for hot bending tests, also. Such tests are 
employed to make sure that the steel is not cold short or hot short and, 
in a way, to indicate the ductility of the metal. 


SECTION III. 

THE TESTING OF THE HIGHER CARBON AND HEAT TREATED STEELS. 

Kinds of Tests Applied to the Higher Carbon and Heat=treated 
Steels: For testing the class of material referred to under this heading, 
a large number of different tests have been devised. These tests may be 
classified under the headings of tensile tests, compressive tests, torsional 
tests, impact tests, and hardness tests. Of these, the tensile, impact, and 
hardness tests are the ones most frequently met with, and will, therefore, 
be described later. Of the others the torsional test is perhaps the most 
important, as it is largely used in the testing of steel for automobiles. 
It consists in twisting a small round specimen of steel held in a suitable 
machine until rupture occurs. In it a test piece of standard size is used, 
and values for this piece corresponding to the elastic limit and ultimate 
strength, but expressed in inch-pounds, are obtained very much as in the 
tension test; the amount of distortion, however, is given in degrees. The 
compression test is carried out by means of a machine similar in con¬ 
struction to the pulling machine. The test piece may be in the form of 
a small cylinder or a one inch cube. The elastic limit under compression 
is determined, and the distortion is indicated by the decrease in length. 

The Tensile Test: The test for determining the tensile strength of 
the higher carbon and heat treated steels is carried out in a manner similar 
to that for the softer steels, but since the material is so much stronger and 
the items made from such steels do not lend themselves to the same method 
of sampling, the test piece is much smaller than that employed in the case 
of structural steels. This specimen is in the form of a small round, as 





HIGH TENSILE STEELS 


309 


shown in the accompanying figure, and is often obtained by boring with 
a hollow drill about midway between the center and outside surface of 
the section sampled. 



K-- 4 „----- ? 


Fig. 47. Drawing Showing Usual Size and Form of Test Piece Used in Pulling High 

Tensile Steels. The ends may be of any form desired but the central machined 

portion must be as shown in the figure. 

Impact Test: While several different types of machines for measuring 
the resistance of steel to impact have been invented, the results obtained 
with any of these machines so far have not been considered very reliable, 
as widely varying results may be obtained on the same steel tested on 
the same machine. In practice, therefore, the nearest approach to an 
impact test is what is commonly and correctly called the drop test. It 
is applied to full size pieces of rails, to axles, and to other sections. It 
consists in allowing a specified weight to drop from a specified height a 
specified number of times upon the sample, which is supported at two points 
on a heavy anvil or block resting upon strong springs. All three of these 
factors may vary greatly with different classes of material and with the 
different ideas of the engineers. While it does not measure absolutely 
any property of the metal and is to be considered as comparative or 
qualitative only, it is, nevertheless, one of the most useful of practical tests, 
for it determines, in a crude way, the ductility and homogeneity of the metal 
and its resistance to shock. In the case of axles and other round bodies, 
the deflection from a given weight may be kept constant for different sizes 
by varying the height, for since the strength of such a section varies as 
the cube of the diameter, for equal deflections, the height varies as the 
cube of the diameter of the specimen at its center. 

Hardness Tests: The best known and the most widely used instru¬ 
ments for measuring the hardness of metals are the Shore scleroscope and 
the Brineli ball testing machine. The Shore instrument consists of a small 
diamond-faced tup enclosed in a glass tube which is provided with a suction 
bulb, whereby the tup may be raised to the top of the tube and dropped from 
a definite and fixed height. To make a determination, the instrument is 


















310 


TESTING OF STEEL 


held in the vertical position with the lower end resting upon a smooth 
and highly polished spot on the surface of the metal to be tested, when 
the tup is allowed to drop by compressing the bulb. The height of the 
rebound, which may be read on a scale inscribed on the tube, is taken as 
a measurement of the hardness. Notwithstanding the fact that the results 
obtained by this instrument are sometimes very erratic, especially if the 
surface of the different spots tested have not been properly and uniformly 
polished, it is a valuable instrument for comparing the surface hardness 
of different parts of a body that is too large to be tested in any other 
way. It also possesses the advantage that the tests may be made upon 
the finished article without injury to the article itself. 

Brinell Hardness: The Brinell hardness test measures the ability of 
the metal to resist penetration by a small ball when propelled by a gradually 
applied force. It consists in pressing a hardened steel ball into the surface 
of the specimen under test by means of a fixed load gradually applied. 
The instrument consists essentially of a small hydraulic press, which is 
operated by a small hand pump and is provided with a pressure gauge 
for reading the pressure, and a special contrivance for automatically 
holding the pressure when it has reached a maximum of 3000 kilograms. 
The piston of the press, which acts vertically downward, is provided 
on its end with a hardened steel ball, ten millimeters in diameter, by 
means of which an impression may be made on the smooth surface of the 
specimen, which rests on a firm but an adjustable base. The operation of 
the instrument is very simple. The specimen, the surface of which has been 
planished with a file, a whetstone, emery wheel or similar means, is laid on 
the base and is then brought in contact with the ball by turning a small 
wheel for adjusting the base, or platform. By operating the hand pump 
until the maximum pressure is attained and maintained for about one 
half minute, the steel ball is pressed into the surface; then the pressure 
is relieved, the base is lowered, and the diameter of the impression 
made in the specimen is measured by means of a microscope fitted 
with a millimeter scale, vernier, and cross hair. From this diameter the 
spherical area of the impression may be calculated, which, divided into the 
maximum load of 3000 kilograms, gives the hardness number. The formulas 
for making these calculations may be combined into a single formula, thus: 



2^r(r 


where P=3000 Kilograms pressure, r=5 mm., radius of the ball, D=diameter 
of the impression, and H=the hardness number. In practice it is most 
convenient to have a table, such as that shown below, prepared, from 
which the number may be obtained direct from the diameter of the 
impression. 






BRINELL TEST 


311 


Relation of Brinell Number to Tensile Strength: It is both a 
curious and a significant fact that the Brinell hardness number bears a 
close relation to the ultimate strength, as may be seen from an inspection 
of the following table, which was prepared only after comparing results 
obtained upon thousands of specimens, to which both the Brinell and the 
pulling tests had been applied. This relation, it will be observed, is 
approximately 500, and holds for all grades of carbon steel whether they 
be heat treated or in their natural state as forged or rolled. For this 
reason the Brinell test is applicable to the rapid testing of steel from which 
samples for the tensile test cannot be obtained. 

Table 47. Brinell Hardness Numbers and Estimated Tensile Strength 
for 3000 Kilogram Pressure on a 10 MM. Ball Testing Machine. 


A 


Diam. 
of Im¬ 
pression 
in m/m 

Hard¬ 

ness 

Number 

Ultimate 
Pounds 
per Sq. In. 

Diam. 
of Im¬ 
pression 
in m/m 

Hard¬ 

ness 

Number 

Ultimate 
Pounds 
per Sq. In. 

Diam. 
of Im¬ 
pression 
in m/m 

Hard¬ 

ness 

Number 

Ultimate 
Pounds 
per Sq. In. 

2.00 

946 

465100 

3.35 

332 

162700 

4.70 

163 

80100 

2.05 

878 

442100 

3.40 

321 

157800 

4.75 

159 

78300 

2.10 

857 

421600 

3.45 

311 

153100 

4.80 

156 

76600 

2.15 

817 

402000 

3.50 

302 

148600 

4.85 

153 

74900 

2.20 

782 

383700 

3.55 

293 

144300 

4.90 

149 

73300 

2.25 

744 

366600 

3.60 

286 

140200 

4.95 

146 

71700 

2.30 

713 

350600 

3.65 

277 

136200 

5.00 

143 

70200 

2.35 

683 

335700 

3.70 

269 

132400 

5.05 

140 

68700 

2.40 

652 

321600 

3.75 

262 

128800 

5.10 

137 

67200 

2.45 

627 

308400 

3.80 

255 

125300 

5.15 

134 

65800 

2.50 

600 

295900 

3.85 

248 

121900 

5.20 

131 

64500 

2.55 

578 

284300 

3.90 

241 

118700 

5.25 

128 

63100 

2.60 

555 

273300 

3.95 

235 

115500 

5.30 

126 

61800 

2.65 

532 

262900 

4.00 

228 

112600 

5.35 

124 

60600 

2.70 

512 

253100 

4.05 

223 

109700 

5.40 

121 

59400 

2.75 

495 

243800 

4.10 

217 

106900 

5.45 

118 

58200 

2.80 

477 

235000 

4.15 

212 

104200 

5.50 

116 

57000 

2.85 

460 

226600 

4.20 

207 

101600 

5.55 

114 

55900 

2.90 

444 

218700 

4.25 

202 

99100 

5.60 

112 

54800 

2.95 

430 

211200 

4.30 

196 

96700 

5.65 

109 

\ 53700 

3.00 

418 

204100 

4.35 

192 

94400 

5.70 

107 

52700 

3.05 

402 

197300 

4.40 

187 

92200 

5.75 

105 

51700 

3.10 

387 

190800 

4.45 

183 

90000 

5.80 

103 

50700 

3.15 

375 

184600 

4.50 

179 

87900 

5.85 

101 

49700 

3.20 

364 

178800 

4.55 

174 

85800 

5.90 

99 

48800 

3.25 

351 

173200 

4.60 

170 

83900 

5.95 

97 

47900 

3.30 

340 

167800 

4.65 

166 

82000 



% 


- —- : —=Hardness Number. 

Area of Impression 

Tensile in Kg. per Sq. MM.=Coefficient .346 x Hardness Number. 
Factor to Convert Kg. per Sq. M/M to Lbs. per Sq. In.=1422.3 











































312 


MECHANICAL TREATMENT 


CHAPTER II. 

THE MECHANICAL TREATMENT OF STEEL. 

SECTION I. 

METHODS AND EFFECTS OF MECHANICALLY WORKING STEEL. 

Methods of Shaping Steel: After the separation of the metal from 
its ores, which in modern practice is accomplished by means of either the 
'blast furnace or a form of electric furnace, and its purification in the 
Bessemer converter, open hearth, puddling furnace, or electric furnace, the 
third step in the metallurgy of iron is the reduction of the large bodies 
of metal thus produced to the various forms and sizes required by the 
many uses to which it is to be put. In general this shaping may be brought 
about either by pouring the metal while in a molten state into moulds, 
which act is called casting, or by mechanically working it. Since by all 
the methods of purification, puddling excepted, the metal is obtained in 
the fluid state, casting would appear to be the simplest and cheapest 
method of shaping; but for forming articles of very small section, it is 
evident that this method is impracticable; nor is it used, unless unavoid¬ 
able, to form the larger sections in which the mechanical properties of the 
metal must be devoloped to the highest degree. Some shapes on account 
of their size or their intricate design require casting, while others are cast 
because they require no great strength in service and the cost of production 
only is to be considered. A lack of strength and ductility in castings is 
inherent, and is due to chemical and physical phenomena that accompany 
the solidification of the molten metal, something about the nature of which 
will be explained later in connect ion with the cooling of ingots. Suffice it 
to say now that the weakness of castings is due chiefly to any or all of 
three causes, namely, blow holes, segregation, and crystallization. 

Benefits of Mechanical Working: On the other hand, mechanical 
shaping improves the quality of the metal by forcing its particles into 
more intimate contact, closing up cavities, and by refining its crystalline 
structure, and so has important functions aside from the mere reduction 
to form and size. The change in properties that may be attributed to the 
process of mechanical working is a marked one, for the strength, ductility 
„and hardness are all affected. Of these properties the strength is always 
increased by the working, the hardness may or may not be markedly 
increased, while the ductility, i. e., elongation and reduction in area, may 
be either increased or decreased, depending on the conditions of the 
working. The amount of change in each of these properties for a given 
steel of a certain chemical composition is affected by the amomit of work 
done and by the temperature at which the working is carried on. 





313 


HOT AND COLD WORKING 


Hot and Cold Working: In the mechanical treatment of the metal, 
the first distinction to be made is that of hot and cold working. The 
study of metallography has shown that the term hot working of steel should 
be applied to the working of it at temperatures above its upper critical 
range, the temperature of which varies, inversely with the carbon content, 
from 700° to 900° C., while all work done at temperatures below this 
range should be called cold working. It will be shown in the next part of 
this book that a sharp change in structure due to working takes place as 
the critical temperature of the steel is passed. This change is due mainly 
to the fact that above this range iron exists in an allotropic crystalline 
form, the gamma form, in which carbon dissolves to form a homogeneous 
mixture, while below it the metal assumes the alpha form and is a crystal¬ 
lized aggregate of ferrite and cementite. A metallographic examination 
of specimens shows that the result of working this aggregate structure is 
one of permanent distortion, or strain, and one in which the properties of 
the metal are deeply affected, as indicated by the different physical 
tests. The elastic limit, tensile strength, and hardness are increased, 
while the ductility is reduced. The extent of this change varies according 
to the temperature, and is most marked when the working is done 
at or below atmospheric temperatures. Cold working becomes less 
effective as the critical temperature is approached, which is due to the 
increase in molecular energy and the resulting loss of rigidity by the solid. 
It should be noted that below the critical range no refinement of the granular 
structure can be accomplished by working. In hot working, the grain size 
is decreased, and the metal is subject otherwise to mechanical refinement, 
the extent of which depends not only on the amount of work done and size 
of the section but on the temperature above the critical range at which 
the work is finished. However, if, after a working, the metal be heated 
above this finishing temperature, as is often the case in the actual rolling 
of steel, the grain refinement of the previous working may be partly or entirely 
destroyed, depending upon the temperature to which the piece is reheated. 
Owing to the plasticity of the metal at the higher temperatures, the dis¬ 
tortion due to working above the critical range does not produce a per¬ 
manent strain in the structure of the solid. After each distortion the 
structural components, the crystals or grains, are free to return to the shape 
and arrangement peculiar to their state of equilibrium. Besides, since the 
steel takes on a new structure and a new condition is born upon cooling 
through the critical range, any internal tension set up by the working 
is relieved by the rearrangement that takes place in passing through this 
range. This fact gives another reason for the superior quality of hot 
worked material over castings, which are subject to immense internal 
tension, or stresses, set up by physical phenomena that accompany the 
solidification and by the forces of contraction due to the unequal rates of 
cooling between the exterior and interior of a casting. Such severe stresses 
do not occur in hot worked material. Referring to the more common prac- 





314 


MECHANICAL TREATMENT 



1. Cast steel. Carbon .35 per cent. Magnified 100 
diameters. 



3. Cold worked hypo-eutectoid steel. Carbon 0.30 
per cent. Magnified 100 diameters. 




Fig. 4S. Showing Effects of Working 







HOT AND COLD WORKING 


315 





2. Hot worked steel. Carbon 0.50 per cent. Finishing 
temperature high. Magnified 100 diameters. 



4. Hot worked steel. Carbon 0.50 per cent. Fin 
ishing temperature low. Magnified 100 diameters 


/ 


upon the Grain Structure of Steel. 






316 


METHODS OF WORKING 


tice of working the steel on its initial heat, that is, working it before it 
has cooled much below the temperature of solidification after having 
been cast subsequent to manufacture in the molten state, careful study 
has developed the fact that it matters little, so far as the effect on the 
refinement wrought by the working is concerned, whether the ingot has 
or has not been allowed to become completely cold before being brought 
to the required temperature for working. Therefore, while the idea is 
contrary to the popular notion, the primary object in the steel workers mind 
should be the improvement in quality of the material he is working, 
while the shaping of the material may be looked upon as a secondary 
object. 


SECTION II. 

SUMMARY OF THE HISTORY AND PRINCIPLES OF WORKING STEEL. 

The Three Methods for Mechanically Working Steel: With 

reference to the manner of applying pressure to steel during mechanical 
working there are three possible methods; namely, hammering, pressing 
and rolling, all of which are extensively used at the present time. The 
shaping of steel by either of the first two methods is called forging. As 
an introduction to the study of the rolling of steel, a brief resume of the 
history, principles, and effects of each of these methods will not be out 
of place and may be found quite interesting. 

Hammer Forging: Hammering was the first method employed by 
man in shaping'the metals. The first forging was done by hand hammers 
wielded by the workmen. The first power hammer, known by the name 
of tilt hammer, was built in England, and was a crude affair com¬ 
pared with the steam hammers now used. It consisted of a beam of wood 
hinged at one end and provided with an iron hammer head at the other. At 
an intermediate point, engaging cams on a revolving shaft alternately 
raised the free end and allowed it to fall on a bottom die fixed upon a suitable 
foundation. Thus the top die could be parallel to the bottom die in only 
one position, and the larger the piece to be forged the less power there 
was available to forge it. The first steam hammer was built in France 
in 1842. It consisted of a two piece frame constructed so as to support, 
directly over a die or anvil, a steam cylinder, to the piston rod of which 
was attached a tup, or hammer head. By admitting steam into the cylinder 
below the piston, the hammer was raised for a distance equal to the stroke 
of the cylinder, and then allowed to drop upon the anvil or bottom die. 
This hammer had the advantage of always keeping the top and bottom 
dies parallel, but was still lacking in one important particular. Its power 
being derived from the inertia of the falling tup, the hammer had the least 
power when it was most needed, that is, when pieces of large diameter or 
of great thickness were being worked. This fault in the single acting 
hammer was corrected by the invention of the double acting hammer, in 




EFFECTS OF FORGING 


317 


which steam is admitted at the top of the piston and employed on the 
downward stroke as well as for lifting the tup. The first double acting 
hammer was built at Midvale, Pa., in 1888. 

Principles and Effects of Hammering: The principles of the hammer 
are that of an instantaneous application of pressure applied to a relatively 
small area. The strains set up in the metal are compressive and take 
place in a vertical direction in the region below the area subjected to the 
force of the blow. The crowding of the metal into one region, however, 
causes a small portion of the blow to be transmitted in horizontal directions. 
The suddenness of the blow tends to localize the effect and confine the 
refinement to the exterior. This fact results in a high degree of refinement, 
provided the amount of reduction is great or the section worked is a thin 
one, and is one of the reasons why it is possible to make some hammered 
material superior to rolled material. The resistance of the metal to 
deformation under shock, combined with the intermittant action of the 
hammer, makes shaping by hammer a slow process. 

The Forging Press: The press is an English invention, dating from 
the year 1861. It was introduced into this country about the year 1887. 
It consists essentially of a hydraulic cylinder supported by one or two 
pairs of steel columns which are anchored to a single base casting of great 
weight and strength. The ram of the cylinder points downward and carries 
an upper forging bitt vertically opposite a similar lower and stationary 
bitt which rests on the base casting to which the columns are attached. By 
admitting water under pressure to the cylinder at its top the upper pallet 
is forced down upon the material to be forged, which rests upon the lower 
pallet. The pressure is applied slowly and is gradually increased to a 
maximum which may be maintained till the metal yields. By means of 
small auxiliary cylinders the ram is lifted after each application of pressure. 
The pressure exerted by the forging press is very great. In practice it 
is found that the lowest pressure that can be employed to be effective at 
a full forging heat is about 1.2 tons per square inch, but the. pressures 
employed in actual work will often reach 13.26 tons per square inch. 

The Effect of Pressing: The press differs very much from the hammer, 
both in action and the effects produced. Unlike the instantaneous appli¬ 
cation of the pressure as in the case of the hammer, the action of the press 
is so slow that a kneading of the metal takes place, and the strain, instead 
of being confined to the surface, penetrates deep into the material. An 
illustration cited by Messrs Harbord and Hall will serve to demonstrate 
the difference in the effect produced by the two methods of working. 1 

“If tests are taken from the outer parts of a gun forging which has the 
center trepanned out, little difference is found in the strength of the 
material, whether the forging was done under the press or under the 
hammer, provided the latter was sufficiently heavy for its work; the 

JSee The Metallurgy of Steel. Yol. II. Page 855. Published by J. B. 
Lippincott Company, Philadelphia, Pa., 





318 


METHODS OF WORKING 


press showing, if anything, slightly better results. If, however, the test 
pieces are taken from the cores which have been cut out of the center of 
the forgings, the difference in the results is so very marked as to have in 
duced all the best makers of heavy steel forgings to install presses in- 
place of, or in addition to, their large hammers.’' 

Advantages of the Press: Aside from its increased beneficial effect 
upon the material, the press has many advantages over the hammer, some 
of which it may be of interest to cite. The absence of shock in the press 
is a decided advantage both in the construction of the machine and in the 
working of material. The cost of working material under a press is less 
than with the hammer because the output is greater, the press reducing 
faster than the hammer, fewer men and less skilled labor are required, 
and the fuel consumption per ton of output is less. A much greater propor¬ 
tion of the total work put into a press is transmitted to the metal than is 
the case with the hammer. Much of the energy of the latter is dissipated 
through being absorbed by the spring in the anvil block and by the earth. 
For certain work, however, this impact gives the hammer two advantages: 
first, it serves to remove scale; second, it enables the hammer to strike 
forgings in molds with greater ease than the press. The difficulty of 
retaining water under the extremely high pressures required by presses 
gives the hammer an advantage, but this advantage is offset by its greater 
liability to breakage. 

Rolling: Of all the known methods of shaping steel from the cast 
material, that of rolling, as introduced by Henry Cort in 1783, though 
perhaps not producing the best quality in certain classes of product, has 
come to be the most extensively employed. Though Cort is rightly credited 
with being the father of modern rolling, the use of this principle in shaping 
metals antedates his mill by many years. Thus, there are records to 
show that in the year 1553 a Frenchman employed rolls to produce sheets 
of uniform thickness for the stamping of gold and silver coin. In Sweden 
rolls were employed to produce certain steel sections prior to the year 1751, 
and even at that time the assertion was made that as much as twenty 
times more bars could be reduced in a given time than could be shaped 
under the tilt hammer of those days. This fact, coupled with the great 
efficiency of the rolling method, is responsible for the universal adoption 
of rolling as the favorite method of shaping. The rapid growth in the 
production due to the ever increasing demand for iron and steel-, made it 
imperative that the most rapid method of shaping be employed. From 
the days of Cort to the present time, the rolling mill has kept pace with 
the growth in production and has passed through a surprisingly rapid 
process of development, not only in size and power but in design and in 
the shapes of sections turned out. This development, together with the 
introduction of numerous appliances for handling the material mechanically 
during the rolling, has multiplied the capacity of the mills many times. 




PRINCIPLES OF ROLLING 


319 


Some modem mills, like the rod mill, will now turn out a hundred times 
as much tonnage in a given time as a mill of the same size and working 
on rods of the same size could have done fifty years ago. 

Principle and Effect of Rolling: The process of shaping steel by 
rolling consists essentially of passing the material between two rolls revolv¬ 
ing at the same peripheral speed and in opposite directions, i. e., clockwise 
and counter clockwise, and so spaced that the distance between them is 
somewhat less than the height of the section entering them. Under these 
conditions the rolls grip the piece of metal and deliver it reduced in section 
and increased in length in proportion to the reduction, except for a slight 
lateral spreading which is almost negligible in some sections. The extent 
of the spread will be found to depend mainly upon the amount of reduction 
and width of the piece. Thus in rolling plates, the total spread may be 
less than that of the first pass in the reduction of two-inch billets, 
especially if the percentage reduction in sectional area in the latter is 
great. The nature of rolling may be best explained by means of the follow¬ 
ing diagram. 


F 



Fig. 49. Diagram Illustrating the Nature of Rolling. 

Let O A C and O' A' C' be two plain motionless rolls which are being 
forced into the bar AA' E'E by means of pressures applied vertically from 
F and F'. The force exerted by the resistance of the bar will act along 
the radii of the rolls, as OA, OC, O'A', and O'C'. The resultant of all 
these forces will be in the vertical lines O B and O'B'. Vertical compression 
of the metal will, however, occur only between the points B and B'. At 
all the other points between AC and A f O' the metal is forced away from 
the rolls and the bar is elongated. If now the rolls are made to revolve, 
the lower one in a clockwise direction and the upper in a counter clockwise 
direction, the piece is reduced in size and elongated as shown by figure 
A A' D'D. This turning of the rolls introduces a second force, which 
acts in the direction of tangents to the arcs AB and A' B ; and is equal to 
the force of friction and therefore proportional to the pressure between the 
rolls and the piece. The result of this force is to subject the piece to a 










320 


METHODS OF WORKING 


longitudinal pull in the direction of B to D, this pull being at its maximum 
at B and at its minimum at A. The compression, however, is at its 
maximum at A and its minimum at B. The net result of this double action 
is to cause the metal to flow forward so that the piece, reduced in size, 
is delivered at a higher velocity than the peripheral speed of the rolls, 
the evidence for which is found in the fact that the marks on the piece 
caused by a depression or elevation on the rolls is farther apart than the 
circumference of the rolls. A slight retardation of the forward speed of the 
piece on the entering side may take place,' but this point has not been 
very well established as a fact. 

Rolling Compared with Hammering and Pressing: It is a very 

difficult matter to institute a fair comparison between the effects of rolling 
with those of hammering or pressing. Each method has a field of its own 
with rather well defined boundaries. Thus, many shapes are so intricate in 
design that rolling them is out of the question, and so they must be formed 
under the hammer or the press. A crank shaft and a hammer head serve 
as examples of these classes of shape, which can be produced in no other 
way, unless by casting, when they would then be lacking in the strength, 
ductility and soundness imparted by working. That the hammer and the 
press are both under better control than rolls is evident, and being slower 
and more expensive to operate than rolls, these tools are used on material the 
cost of manufacture of which is a secondary matter. Hence, extraordinary 
care and attention is given to all phases of the working of forged articles. 
Rolls on the other hand are cherished for their speed, and tonnage is always 
a factor in rolling. There is, however, a small area in which the field of 
operation of all three instrumentalities overlap, as in the shaping of billets 
or blooms from ingots. In working these billets the different effects 
produced by the three methods become visible as the piece is shaped. 
When an ingot is hammered, the shape imparted to the section is very 
liable to look like A in Fig. 50. If the blows are light and delivered at 
high velocity, the upper surface only will be elongated as shown at B in 
the figure. These facts show that the impact is almost entirely absorbed 
by the surface of the metal, and to obtain the best effect from hammering 
it is necessary to continue the work until the section has been reduced to 
one of relatively small size. The deeper penetration of the work of the 
press is shown by the rounded corners of the section represented by the 
figure at C. Any cavity at the center of the piece is closed under the 
action of the press, whereas the tendency of the hammer would be to enlarge 
it. The effect of rolling is influenced very markedly by the temperature. 
In the first place the temperature, in order to secure the greatest efficiency 
from the rolls, is likely to be higher than that required for either hammering 
or pressing. In a piece uniformly heated, the flow of the metal is slightly 
faster at the two surfaces than in the center in the smaller sections, while 
in larger sections the flow at the surface may be very much greater. The 
effect of the additional plasticity imparted by even a slight rise in tern- 





COMPARISON OF METHODS 


321 


perature upon the flowing properties of the metal is plainly visible in the 
results obtained in rolling ingots under the two conditions as illustrated 
by the figures at D and E. The fishtailing of the piece represented at D 
shows that the flow of the metal is faster at the surface due to the lack 


Hammering A 



Heavy Strokes 



Light Strokes 


Pressing 



Rolling 



Center cooler than surface Center hotter than surface 

Fig. 50. Diagram Illustrating the Effects of Hammering, Pressing and Rolling. 

c 


of plasticity at the colder center. The reverse of these conditions is shown 
at E with the corresponding difference in effect. In this case the effect 
of the working has penetrated to a much greater depth and extent than 
in the previous case. The amount of draught and the speed of rolling are 
also important factors in producing these effects, a more thorough dis¬ 
cussion of which will be taken up later. 

Rolling and Pressing Ingots: The notion most prevalent among 
steel men, however, is that the tendency of rolling is to produce a more 
superficial effect than either hammering or pressing. That this notion is 
correct with respect to pressing is indicated by the precautions taken in 
casting large ingots for armor plate that is to be rolled. Figure 51 shows 
the difference in shape of ingots for the press and for the rolls. The concave 
and diamond shaped sides of the ingot for rolling are formed to prevent 
the loss due to fishtailing, as already explained. Under ^he press the two 
surfaces of a square sided ingot are slightly rounded, but, in rolling, a 
square sided ingot w r ould make a concave sided plate which in many cases 
progresses to such an extent as to cause actual overlapping. It is admitted 
by nearly every one, however, that with very slow rolling and carefully 
regulated temperature that the quality of rolled material may be made 
the equal of that reduced under the press. 



For Pressing For Pressing For Rolling 

Fig. 51. Shapes of Ingots for Pressing and Rolling Armor Plate. 




















322 


THE ROLLING MILL 


CHAPTER III. 

ESSENTIALS OF ROLLING MILL CONSTRUCTION AND 

OPERATION. 

SECTION I. 

THE ROLLS—THEIR PREPARATION AND ARRANGEMENT. 

Parts and Equipment of the Simplest Type of Rolling Mill: After 

the rolls, themselves, two in number in the simpler types of mill, the next 
most essential part of the mill are the chocks or bearings which support 
the ends of the rolls and permit them t,o be turned without displacement. 
The chocks in turn are kept in place by means of the housings, which 
together with the adjusting screws also furnish a means by which the 
distance between the rolls is regulated. These parts constitute a stand 
of rolls. The housings are bolted to shoes which rest upon a firm foun¬ 
dation, to which they are always securely bolted. Next in im¬ 
portance are the parts which connect the mill with the driving shaft. 
First, there are the spindles that transmit the power from the pinions 
to the rolls, to both of which they are connected by means of loosely fitting 
coupling boxes. The pinions, supported in housings similar to the roll 
housings, are gears, one of which is driven through a driving spindle in line 
with one of the rolls. They serve to impart opposite motions to the rolls. 
The last part of equipment essential to the mill is the prime mover, which 
in modern mills may be a steam engine or an electric motor. As to other equip¬ 
ment, reheating furnaces are first in importance. Large mills must also be 
provided with roll tables for handling the material. A discussion of the 
driving apparatus is an engineering subject which lies beyond the intended 
scope of this book and will receive no further mention here. .All the 
remaining parts, however, should be studied somewhat in detail. 

The Rolls and Their Parts: Of the essential parts of the rolling 
mill the rolls furnish a subject of great interest. There are three parts to 
a roll; namely, the body, which is the part on which the rolling is done; 
the necks, or the parts which rest in the chocks and furnish the surface 
upon which the pressure is applied for reducing the size of the piece; and 
the wobblers, one at the outer end of either neck or of both necks, which 
are formed by notching the prolongation of the neck of the roll. Over the 
wobblers the coupling box for driving the roll is fitted. In the case of 
plain rolls, such as are used for rolling plates and, in part, for other flats, 
these are the only parts of the roll. In the case of rolls for other material, 
grooves are cut into the surfaces of the rolls to form the section required. 




THE ROLLS 


323 


A groove in one of the rolls or a combination of grooves in the two rolls, 
which at the line of contact forms an opening corresponding to the shape 
of the section desired, is called a pass. The three most common passes 
are shown in the accompanying figure. 



I Open Box II Closed Box . Ill Diamond (90°) IV Gothic 


Fig. 52 . Showing Different Types of Passes For Roughing and Semi-finishing Mills 
I, III and IV are spoken of as open passes while II is called a closed pass. 
In the closed pass the piece is buried in one of the rolls so that three sides are 
enclosed by the groove A, the fourth side being closed by the tongue or former 
D, on the other roll. Collars are represented at C and Cb Passes I and II 
are commonly spoken of as box passes, while III is called the diamond pass, 
and IV the Gothic pass. 


The Manufacture of Rolls is a separate industry, and the art of roll- 
making is not widely known even among the users of rolls. When the work 
the rolls have to do is considered, together with their effect upon the product 
of the mill, the importance of good rolls is better appreciated. Most rolls 
are castings, yet they must be ductile to withstand the shock produced 
as the piece enters them; strong to resist sufficiently the great pressure 
applied to their ends; hard to give them good wearing qualities; and sound, 
so that they may not develop surface defects which would leave their marks 
on every surface rolled on them and cause the material to be rejected. 
To secure these qualities the best of materials and the greatest of skill 
are required in their manufacture. The materials are of three kinds, namely, 
cast iron, steel and alloy mixtures. From these materials four kinds of 
rolls are produced. They are known as sand rolls, which are made of pig 
iron; chilled rolls, also of cast iron; steel rolls, made of steel by casting; 
and “adamite” rolls, which is a trade name for a metal produced by mixing 
steel with pig iron containing certain percentages of chromium and nickel, 
or by mixing steel and the ferro alloys of these elements with the proper 
amount of an ordinary pig iron of high grade. As an example of how rolls 
are made, some of the processes as carried out by one of the leading manu¬ 
facturers of rolls will be briefly described. 

The Sand Roll: Sand rolls are cast in a sand mold. The sand used 
is a loamy sand of a special kind obtained only from deposits left in old 
water courses. This sand contains sufficient clay intimately mixed with 
the silica to form a firm bond and yet be refractory enough that it will 
not fuse at the temperature of the molten iron. The mold is prepared by 
ramming this sand, moistened a little, into a half flask, and then sweeping 































































































































324 


THE ROLLING MILL 


the sand from the half flask with a sweep, the outline of which is similar 
to the contour of the roll. Two such half flasks are required for each roll, 
each one containing one-half of the roll divided longitudinally. After 
sweeping and smoothing, the half molds are coated inside with a plumbago 
or other carbonaceous dressing and carefully dried. Just before casting, 
these two parts of the mould are firmly clamped together and are set in 
a vertical position for pouring, for which purpose a casting pit is provided 
for large rolls. Thus, one end of the roll forms the bottom of the casting, 
the other end the top. The top is capped by a cope to provide a deep sink- 
head, which is cut from the roll after casting. The gating to the mold 
enters the flask at the bottom neck of the roll and on a tangent, so that 
a swirling action is imparted to the molten metal as it rises in the mold. 
In this way all dirt and other foreign matter is forced to the center, which 
condition insures the outer portion of the roll will be composed of clean 
metal. 

The Materials Used in Sand Cast Rolls are charcoal iron and roll 
scrap. The mixtures are melted in coal fired reverberatory furnaces. 
The bath, sealed off from outside air, is separated from the grate by a 
bridge wall, over which a non-oxidizing flame sweeps and furnishes the heat 
for melting. In the melting a little carbon, silicon, and manganese are 
removed from the metal, and by the time the charge is melted a highly 
silicous slag has formed, which protects the metal from any further action 
that might be produced by the flame. As soon as the metal is melted, 
fracture tests are taken, by means of which the metallurgist in charge 
is able, from long experience, to determine when the bath is of the right 
composition to produce the kind of roll desired. The molten metal is 
tapped from the furnace into a small tilting ladle, which is carried by 
overhead crane to the molds, and the metal is poured into the gate over the 
lip of the ladle. The pouring is very rapid and must be continuous, as the 
slightest interruption would ruin the casting. After the metal has 
solidified and cooled sufficiently, the mold is removed, and the roll is 
cleaned of the adhering sand, when it is ready to be machined to the size 
and shape required. 

Chilled Rolls: Rolls of the chilled type are made up of three layers 
of metal, each of which represents a type of the same original metal. The 
interior of these rolls is composed of grey iron, which is enclosed by a 
cylinder of mottled iron, and outside of this a similar layer of white iron, 
called the chill. This composite structure is procured by taking advantage 
of the peculiar properties exhibited by pig iron on cooling from the molten 
state. In this state iron holds in solution all the carbon which it contains 
at a given temperature. In cooling some of this carbon separates in the 
form of crystals of graphite, which is distributed throughout the mass; 
the remainder is spoken of as combined carbon, the effect of which is to 
increase the hardness of the metal. The separation of the graphite depends 
mainly upon the rate of cooling, so that if the iron is cooled very suddenly 




CHILL ROLLS 


325 


all the carbon may be retained in solution as combined carbon, which 
rendiis a chilled iron that is dense, white, intensely hard, and capable of 
receiving a very high polish. In making these rolls only the body of the 
roll is given a chill. This chilling of only a part of the roll is effected by 
making that part of the mold corresponding to the necks and wobblers of 
sand,, while that part destined to form the body is made up of a heavy 
cast iion ring, usually built up in sections which are carefully turned at 
the joints and bored out true inside. After giving the inside of the mold 
a coating of the carbonaceous wash, they are warmed to remove moisture, 



The line in the cut marks the limit of clear chill. When depth of chill is 
designated, it is assumed to mean clear chill. 

Fig. 53. Method of Measuring Depth of Chill on Rolls. 


then assembled, and the casting is made as for sand rolls. The rapid 
cooling, caused by the absorption of the heat by the cold casting in contact 
with the molten metal, causes the chill on the outer surface of the roll, 
the depth and hardness of which is controlled by varying the composition 
of the molten iron. Chilled rolls, once they are formed, cannot be softened 
or hardened by heat treatment, as such treatment would destroy the chill 
A patented chill is now in use. It is made in the form of a ring com¬ 
posed of segments of solid metal on the inside and a water cooled ring 
on the outside. This construction has the effect of causing the mold to 
become smaller as it is warmed by the heat from the molten metal, thus 
subjecting the roll to a high pressure, which is said to give a more even 
chill and a denser and tougher material than the common chill. The chill 








326 


THE ROLLING MILL 


is measured by the least depth of clear chill as shown in the accompanying 
photograph, while the analysis of each of the three regions here depicted 
is given in the following table: 

Table 48. Analysis of Different Parts of a Chilled Roll. 

TOTAL COMB’D. GRAPH. 

CARB. CARB. CARB. SIL. SUL. PHOS. MANG. 


Chill. 3.00 3.00 .... .90 .04 .200 .25 

Mottled. 3.00 2.25 .75 .90 .04 .200 .25 

Grey. 3.00 1.00 2.00 .90 .04 .200 .25 


Difficulties in Making Chilled Rolls: The greatest of skill and 
experience are required in the making of chilled rolls. The process of 
chilling causes the different parts of the roll to cool at different rates and 
sets up stresses in the casting which make it liable to crack and break. 
The range of temperature at which the metal may be poured is very narrow, 
while a very slight change in the chemical composition of the metal will 
sometimes produce a marked effect upon the chill, changing both the depth 
and the hardness. The size of the roll also affects the nature and extent 
of the chill. Besides, the roll in use is subject to great pressure, uneven 
stresses, uneven heating, over heating, and sudden cooling, all of which 
tend to cause the chill to crack and spall. This tendency to spall is over¬ 
come by the manufacturer to some extent, but careful handling of the roll 
in use is essential also. Large rolls are especially difficult to cast properly. 
The largest chilled rolls are made for rolling plates, and a ve^ tough 
chill is required. The chills for one of the largest of these rolls weighs 
105,000 pounds and the roll itself requires 80,000 pounds of metal to cast 
it, while the total length of the mold is twenty-three feet. A large 
percentage of these rolls are lost in casting, due to the cracking of the roll 
at places where the different sections of the chill are joined. Small chilled 
rolls are used in guide, rod, hoop and bar mills, and for a variety of purposes, 
but chilled rolls for shapes are very difficult to make owing to the fact that 
the collars in such rolls are liable to bind in the chill and crack off. All 
these factors tend to make chilled rolls very expensive, but a much greater 
tonnage is obtained from them than from any other kind, and their use is 
imperative where a very fine finish is required to be imparted to the product. 

Steel Rolls are cast in sand in much the same way as sand rolls. In 
this case, however, ganister sand mixed with a little fire clay to act as a 
bond is used, because the higher temperature of molten steel will heat 
any but the most refractory sands to their fusion point. Steel rolls are 
stronger and more ductile than sand rolls. The deflection of a steel roll 
under a given load is only about half as much as that of a common sand 
roll. Besides, they may be annealed, when they become almost unbreak¬ 
able. They cannot be permanently hardened, because any hardening by 
heating and quenching is removed by contact with the hot metal, the heat 
from which produces the same effect as a drawback. On account of their 








ROLL DESIGNING 


327 


unavoidable softness, then, steel rolls do not wear well, and hence cannot 
be used on finishing stands. For blooming mills and roughing stands of 
other mills where great strength is required, these rolls are invaluable, 
and they are used in such stands almost exclusively. Occasionally, where 
a good finish on the product is not required, steel rolls will be used on the 
finishing stands. The material used is, for the most part, acid open hearth 
steels varying from .40% to .65% in carbon content. When steel rolls are 
used for finishing, the carbon content is increased to .85%, and sometimes 
to as high as 1.25%. 

Other Rolls: In an attempt to overcome the defective softness of 
steel rolls and at the same time retain their great strength and toughness 
the alloyed mixture previously referred to as “adamite,” has been 
developed. These rolls are being used with considerable success, and seem 
to hold promise of even greater efficiency. Forged steel rolls have also 
been tried and found to be very satisfactory, but their high cost prohibits 
their use except where exceptional strength is required. 

The Size of Rolls: In length of body, rolls vary from one to seventeen 
feet, and in diameter from seven to forty-eight inches. The largest rolls 
are used on the plate mills, the smallest on the small hand guide mills. 
On account of the smaller surface exposed to pressure, small rolls cut into 
the metal with greater ease than large ones and so require less power to 
do the same work. Therefore, the heavier the rolls, the heavier must be 
the machinery throughout the mill. The factor most important in determin¬ 
ing the size of the roll is that of strength, and for the sake of safety rolls as 
large as practicable will be employed; first cost is of secondary importance. 
The resistance of a plain roll to transverse stress is proportional to the 
cube of its diameter, and inversely proportional to the length of its body. 
The diameter of the roll at the base of the deepest groove determines the 
strength of a grooved roll; so, for grooves of the same depth, one set of 
rolls may be many times stronger than another only one or two inches 
smaller in diameter. The size of rolls is expressed by writing the diameter 
and the length of body in inches, with the X sign between. Thus 42" X 
60" means that the roll is forty-two inches in diameter and sixty inches 
long in the body. 

Roll Design: Designing the rolls was originally one of the duties of 
the mill superintendent, the roll turner or the roller, but the demands 
upon the mills in the way of new sections made it necessary to place this 
work in the hands of men specially trained to the work, so that, now, roll 
designing is a distinct profession. There are few rules in the trade, and 
the roll designer must depend mainly upon experience for guidance. It is 
seldom, therefore, that two roll designers will be found to develop a section 
in precisely the same way. That exceptional ingenuity and extreme 
resourcefulness is required*in this profession is attested by the wonderfully 
intricate shapes these men are turning out, and that, too, with the most 
astonishing accuracy. 




328 


THE ROLLING MILL 


Methods of Procedure in Designing Rolls: Given a new section to 
evolve, the roll designer proceeds in some such manner as follows:—From 
a drawing of the section, if he has decided it is one that can be rolled success¬ 
fully, he will have a templet made of the exact dimensions of the section, 
and from this templet another for the finishing pass in which an allowance 
of about .015 inch per inch of dimension of the finished piece is made for 
contraction of the metal in cooling from the finishing temperature to 
atmospheric temperature. He must then decide on the proper size of rolls 
to use, which determines the mill that is to roll the section. This decision 
made, he has given the approximate size of the billet or bloom from which 
to begin, the number of sets of rolls, and the number of passes in which 
the work must be done. Having given, now, the first and last passes with 
their dimensions, and the total number of passes, he may begin the design 
of the intermediate passes. This he does by drawings which are begun 
by setting off a “construction line” or “pitch line” as it is sometimes 
called. This line locates the center of gravity, or the center of figure, of 
the various passes and is usually placed midway between the axis of rotation 
of the two rolls. 

Difficulties in Designing Rolls: Having drawn the pitch line, the 
roll designer then proceeds to mark off the passes from billet to finishing 
pass, and in doing so he has a multitude of things that must be kept in 
mind, some of which are: 1. The method of shaping is one of squeezing, 
spreading, and bending. 2. The total amount of reduction is best dis¬ 
tributed among the various passes as evenly as possible, excepting the 
finishing, which is reserved to true up the shape. 3. All sides of the 
piece should be thoroughly worked. 4. The piece should not enter two 
successive passes in the same position, as otherwise the metal will be 
squeezed out between the roll and form what is known as a fin. 5. Since 
they weaken the roll very much, deep cuts into a roll should be avoided. 

6. The passes should be so shaped as to eliminate side thrust on the rolls. 

7. A piece will not enter a pass in the rolls if all its dimensions are larger 
than the pass. 8. The thin parts of a section cool faster than the heavier 
parts, and must, therefore, be formed in the last passes. 9. Sections that 
require deep grooves in the rolls are difficult to roll successfully on account 
of the difference in the peripheral speed of the bottom and the top of the 
groove. The part of the roll having the greatest diameter elongates the 
piece more rapidly than the part having the smallest diameter and tends 
to cause the piece to twist and curl on leaving the rolls. This difficulty 
can be overcome by using rolls of slightly different diameters, by raising 
or lowering the center of mass of the piece from the pitch line or by reduc¬ 
ing the amount of reduction on the part that elongates the more rapidly. 
10. The draught on the various parts of a section must be properly 
proportioned, as otherwise the piece will contain waves or be distorted in 
other ways. 11. He must also keep in mind that all kinds of steel do not 
work alike, and what can be done with open hearth steel, for instance. 




TURNING AND DRESSING ROLLS 


329 


would be impossible with Bessemer and vice versa. With these difficulties 
to contend with, even highly experienced roll designers may fail on the 
first trial at a new section. In that case an entirely new set of rolls may 
be required, which adds much to the expense of rolling the section. Besides 
questions, such as those above, that affect the shaping of the material, 
the roll designer is also expected to consider time and cost. So, he will 
endeavor to avoid roll changes or other operations that will delay the work 
or add to the cost of the rolling operation. Thus, it will be found that in 
most mills one set of roughing rolls will be used to produce a great number 
of different sections. This has the effect of giving the designer a fewer 
number of passes with which he forms the shape, and adds much to the 
difficulty of his task. 

Turning the Rolls: Having designed all the passes for the rolling of 
a given section, a set of templets, one or more for each pass, is made. These 
templets are to be used in turning the roll, for which purpose a special set 
of tools may be required. In the roll shop, the rolls are first centered. 
Various methods may be used for finding the center. When this point has 
been located, a lead hole may be made with a ratchet drill, and then widened 
out to the proper angle with a reamer to a depth of about z /i inch. The roll 
is then placed in the necking lathe, when, supported by the center holes, 
the necks may be turned to exact size, or they may be machined to near 
the exact size and finished by grinding and polishing. Since the center 
holes are liable to wear down irregularly if used throughout the process 
of turning, the body of the roll is turned in another lathe in which 
the roll is supported by chocks that fit the necks. Here the roll 
is turned down to size, and the passes cut in to fit the templet supplied 
by the roll designer. When one roll is completed, it is placed in chocks 
higher up in the housing, and the second roll is placed below it, where it 
may be turned with the finished roll as a guide, so that the two parts of the 
passes may be made to fit exactly. With ordinary tools, chilled rolls are 
seldom turned with a surface speed of more than fifty-six inches per minute, 
but with tools made of high speed tool steel this speed may be increased 
to seventy-two inches per minute. Speeds twice as great as these may be 
employed for turning the other kinds of roll. 


Dressing the Rolls: After a set of rolls has been in service a variable 
length of time, the passes become worn to such an extent that they no longer 
produce the section to the required dimensions, and they must then be 
replaced by another set. In most cases these worn out rolls may be turned 
again, or dressed down, so as to give the correct size once more, or if the 
section is of such shape that this refitting is impossible, the passes may be 
enlarged to produce a section similar in shape to the first one but of greater 
weight. This wearing of the rolls is one reason why rolling tolerance is 
required on all materials. 



330 


THE ROLLING MILL 


Types of Mills: Before proceeding farther it may be well to explain 
that there are two main types of mill, referred to as Two=high and Three=> 
high mills. As the names indicate the classification is based on the manner 
of arranging the rolls in the housings, a two-high stand consisting of two 
rolls, one above the other, and a three-high having three rolls thus arranged. 
In all three-high mills, each roll revolves continuously in one direction only, 
whereas in two-high mills the direction of the rolling may be in one direction 
only, or in opposite directions at different intervals, in which case they 
are called reversing mills. 

In the old days before the invention of the three-high mill or the 
reversing engine, if it was desired to pass the bar more than once through 
the same stand of rolls, the catcher returned the piece to the roller by 
placing it on the top of the upper roll, which carried it in the direction 
opposite to that in which it moved at the bottom of the roll. Mills in 
which this practice prevailed were called pull=over or drag=over mills and 
are to be looked upon as the fore-runner of the reversing mill. In the first 
mill of the reversing type a ratchet gear furnished the means for reversing 
the mill. Pull-over mills are still in use, and are the mills most often 
employed for rolling sheets. Another kind of two-high mill is the continuous 
mill, which consists of several stands of rolls arranged in tandem and 
propelled with a single engine. Guide, loop and the so called Cross 
country mills are made up of several two-high stands and one or more 
three-high stands. Guide mills are small hand mills consisting of several 
stands of rolls in a train. They take their name from their having metal 
guides to support the piece as it enters the various passes. In many guide 
mills it is the practice of the catchers, in order to save time, to start the 
piece through each of the passes before it is through the preceding one, 
thus forming a loop. After the institution of this practice it was found 
that the loop could be made by means of a tube or trough, called a 
repeater, and thus dispense with the catchers. Such a contrivance is a 
part of many modern bar and strip mills. The cross country mill is made 
up of several stands of rolls, arranged in trains or trains and tandem sets. 
The bar, propelled mechanically by means of live rolls, transfers, etc., 
must reverse its course two or more times to pass through the various sets 
of rolls from the furnace to cooling tables. These mills represent one of the 
latest and most efficient types. Combination mills are those in which the 
roughing or major part of the reduction is done in continuous rolls and the 
shaping in a guide or loop mill. The Universal Mill is one, which, in addi¬ 
tion to the horizontal rolls, usually arranged two-high but occasionally three- 
high, is provided with vertical rolls, all set in one housing. These mills origin¬ 
ally contained but two vertical rolls on one side only of the horizontal rolls,but' 
in modern mills there are two sets of vertical rolls, one set on either side of the 
horizontal ones. The mill is used for rolling plates and eye bars that 
require rolled edges. Besides these types, there are many special mills, 
usually named from the inventors, such as the Gray mill for rolling beams 




THE CHOCKS 


331 


and H-sections; the Wenstrom mill, a kind of universal mill for rolling bars; 
Sack’s mill for rolling shapes, also a development of the Universal mill; and 
the Schoen mill, which rolls car wheels. Opportunity will be given later to 
become better acquainted with most of these mills. 


SECTION II. 

PARTS OF THE MILL ESSENTIAL TO THE OPERATION OF THE ROLLS - 

The Chocks: As previously indicated, the chocks furnish the bearings 
in which the necks of the rolls turn. They are usually made in two parts. 
The surface in contact with the neck is made of brass, bronze, or white 
metal, which can be replaced as necessary. The use of these alloys is 
necessary in order to reduce friction, which is much less between metals of 
different kinds due to difference in size of the molecules or grains, and to the 
tendency of the softer metals to flow. The approximate composition of 
some of the more common of these alloys is given in the sub-joined table 
of analyses. 

Table 49. Composition of Bearing Metals. 


Name of Alloys 

Red Brass 

% Copper 

85 

% Zinc 

15 

% Tin 

% Antimony 

% Lead 

Yellow Brass. ... 

65 

35 

.. 



Bronze, No. 1... 

85 

• • 

15 



Bronze, No. 2... 

82 

15 

3 



White Metals_ 

0 to 6 


10 to 15 

12 to 20 

65 to 80 


Since 1915, a new white metal composed of lead, about 98.5%, and 
sodium, about 1.5%, has been used with much success. As all these metals 
are soft and not very strong, it is necessary to carry them in castings, which 
are set into the housings. These castings are box-like in shape, each one 
containing on one side a semi-circular groove corresponding to, but larger 
than, the necks of the rolls. In order to reduce their weight, they are cored 
out, and may be made of either iron or steel. 

The Arrangement of the Chocks in two-high mills is a simple matter. 
Two chocks under the necks of the bottom roll, and two similarly placed 
above the top roll furnish the main bearings. In case the top roll is 
adjustable, light bearings must also be placed under its necks to make it 
possible to support this roll. In the heavy mills hydraulic jacks or balance 
weights, placed under the mill, are connected by vertical rods to the lower 
chocks and serve to lift the roll as desired; in the small mills, screw 
bolts extending through the housing serve the same purpose. The exposed 
half of the neck of the lower roll will usually be covered to protect it from 
scale, etc. The arrangement of the chocks in three-high mills is more 












332 


THE ROLLING MILL 


difficult. The simplest way is to place double groove chocks between the 
top and middle and the middle and bottom rolls, and then set them in the 
housings one above the other, so that all the adjusting made necessary by the 
wearing away of the brasses and the material of the rolls, themselves, may 
be made with the large set screws in the top of the housing. But this 
arrangement causes the bottom bearing to wear down rapidly and increases 
the power required to drive the mill, due to the additional friction induced 
on this bearing by the weight of the two upper rolls and their chocks. 
This fault may be overcome in two ways: (1) By making the bottom 
roll fixed and supporting this extra weight on the shoulders of the chocks 
themselves, the distance between rolls may then be regulated with shims, or 
‘diners,” by adding or removing the shims as the bearings wear down. 
(2) A better way, and the one most often employed in modern mills, is 
to make the middle roll fixed, in which case the bottom roll is raised and 
lowered by means of an adjusting wedge attached to a screw in the 
housing which permits it to be moved back and forth with a WTench from 
the outside of the housing. Other methods of adjusting this roll are in 
use also. A method of supporting each roll separately by means of hooked 
screws and cross bars has also been developed, the details of which would 
be unprofitable to study here. In all mills, two-high as well as three-high, 
the top chocks are held down by means of two strong screws which work in 
threaded holes or nuts in the tops of the housings. 

The Function of the Chocks is not only to furnish bearings for the 
rolls vertically but to prevent their movement laterally as well. This 
lateral displacement of the roll is prevented by the inner edge of the bearing 
which is formed to fit against the shoulder of the roll. Adjustments for 
wear in this direction are provided for by adjusting screws which extend 
through the side of the housing and bear on the ends of the chocks. This 
lateral adjustment is a matter of great importance in rolling sections that 
require grooved rolls, the reason for which is self evident. 

The Housings: There are two housings for each stand of rolls, they 
may be made of either iron or steel, the choice of materials depending 
upon the size of the mill, the strength required, and the preference of the 
management. They are castings of an O-orU-form, each enclosing a space, 
called the window, which serves as a receptacle for the chocks. Housings 
may be either closed topped or open topped; in the former, the base, 
the two legs, and the top are all cast in one piece, while in the latter the 
top may form a separate part which can be removed. The base of the 
housing is cast with a projection on each side, the two forming the feet 
of the housing. In the bottom of each foot is cut a groove which fits over 
a girder, called a shoe, running parallel to the rolls. Suitably shaped 
bolts then serve to clamp the foot of the housing to the shoe, which is 
firmly fastened to the foundation by means of long bolts. This method 
permits the housing to be moved laterally, and much facilitates the plumb- 




HOUSINGS AND PINIONS 


333 


ing and lining up of the mill. The tops of the two housings in a set are 
prevented from spreading apart by means of suitable tie rods, or the tops 
of both housings may be cast in one piece. Similarly, tie rods will usually 
be placed at the bottom. Recesses or other openings are cast in the 
inside of each housing to receive the supports for the guards and guides, 
these supports being usually in the form of square bars which extend from 
housing to housing in front of the rolls. The immense pressure applied to 
the roils between the top and bottom of the housing acts as a stretching 
force on the uprights of the housings, and is an important factor in deter¬ 
mining the reduction that can be effected in one pass and also the exactness 
with which the thickness of the piece is controlled. 

The Adjusting Equipment for the rolls has already been located and 
partly described in the preceding paragraphs. In addition it should be 
pointed out that in large mills, in which the top roll is adjusted during the 
rolling, power must be supplied to operate the screws. To provide for the 
transmission of the power, the top part of each screw, which is made square 
or hexagonal for a distance slightly greater than the rise of the roll, passes 
through the core of a pinion. These pinions may then be turned directly or 
indirectly with a horizontal hydraulic cylinder located at a proper height, 
usually on top of the housings of the driving pinions; or, by means of a 
worm shaft and the proper worm gears, the screw down may be effected 
with a small electric motor. In small mills where the adjustment is only 
occasional, the screws will be operated by hand by means of spanner 
bars. In all cases the compression of these screws is unavoidable and 
combined with the stretch of the housings produces the spring of the mill, 
which in some cases is surprisingly great. 

The Pinions: An important part of the mill is the pinions. They 
are broad faced steel gears located between the prime mover and the rolls. 
Their functions are to divide the power, which is delivered by the engine 
or motor through a single shaft or driving spindle, usually spoken of as the 
leading spindle, among the rolls and to control their direction of rotation. 
They run in bearings contained in a pair of housings similar to those for the 
rolls, and should be completely and tightly covered to protect them from 
dust and dirt which would cause them to wear out rapidly. They need 
to be well lubricated, and the present practice of giving them an occasional 
dressing of pine tar, plumbago, and tallow, or other mixture of grease, is 
giving way to the better plan of having the housings cast in one piece so 
as to form an oil bath at the bottom in which the bottom pinion is partly 
submerged. Pinions are of three kinds, based on the arrangement of the 
teeth. In the oldest form the teeth ran straight across the face, but 
eventually it was found that a smoother running pinion results if the face 
be divided into two parts and the teeth of the two halves staggered, i. e., 
set in so that the teeth in one half are in line with the space in the other. 
This design gives an effect like that which would be obtained if the pitch 




334 


THE ROLLING MILL 


were decreased. This scheme was also found to effect a saving in power. 
Still another improvement results from the use of pinions with helical or 
“herring bone” teeth, which also tend to eliminate vibration in the pinions, 
as some parts of the teeth are always in contact, thus making the trans¬ 
mission of the power continuous. This presence of jar when each tooth 
comes into action has an effect on the material, as in certain classes of 
material the old form of pinion was found to produce marks on the bar by 
the jarring of the teeth meshing being transmitted to the rolls. In all 
mills except plate mills, the distance from center to center of the pinions 
determines the size of the mill. 

The Connections: Each roll, except in the case of friction driven 
rolls, is connected to its pinion by means of spindles. They are usually 
made of cast steel and are fitted at each end with wobblers like those on 
the rolls. The comiections between pinions and spindles and rolls and 
spindles are made with coupling boxes. The coupling box is a hollow 
cylindrical casting, the space in which corresponds in section to that of the 
wobbler, one end of the box fitting over the wobbler on the roll and the 
other over that of the spindle. In order to safe-guard the mill, the coupling 
boxes are usually made the weakest part of the mill. In some mills this 
weak spot is the leading spindle, which connects the pinions with the engine 
or motor, instead of one of the coupling boxes. Since the spindle must be 
put in place with the two coupling boxes on it, the length of the spindle 
must be a little more than twice the length of the box. In mills, the top 
roll of which moves up and down through a great distance, the upper 
spindle is thrown out of line horizontally. As it is very difficult to 
operate with a spindle more than 15° out of level, this angle must be kept 
within the allowable limit by increasing the length of the spindle. In 
such cases the ends of the wobblers are cut from a section of a sphere to 
give them the rounded form necessary to permit them to work at different 
angles, and the spindle is supported by means of saddles which rise and 
fall with the roll and hold the spindle in place. 

Guides and Guards: In order to prevent collaring and to insure 
that the piece enters and leaves its pass in the correct position, guides 
are employed. These guides vary in form and size to fit the conditions. 
In some cases they are merely grooved fore-plates; in others they are blunt 
edged plates set up in front of the collars, dividing the space in front of the 
rolls into a series of pigeon holes; in large mills rolling heavy sections, 
they may take the form of grooved rollers; in the smaller mills like the 
guide mills, they are trumpet shaped castings that fit close up to the roll 
and have exit openings to conform to the shape and size of the section 
of the entering piece; in other mills, like the continuous mill, they may 
be so constructed as to twist and thus turn the piece between two successive 
passes. Guides may be employed on both sides of a pass, in which case 
they are designated as entering guides and delivery guides. They are held 




ROLL TABLES, ETC. 


335 


in place by means of the rest bars previously mentioned in connection with 
the housings. Guards are devices employed mainly on the delivery side of 
the mill to control the direction of the piece after leaving the pass. Reversing 
and three-high mills will be provided with guards on both sides of the mill. 

Additional Equipment: In addition to the parts of the mill already 
described, every mill must be provided with suitable appliances for heating 
and handling the materials and disposing of the product. The various 
furnaces for the heating of the raw materials will be described later. As 
to the handling of materials, it is evident that reliance on man power places 
such restrictions upon the size and output of the mill that, in the case of 
certain small mills and of all the larger mills, the appliances for handling 
the materials mechanically are to be considered as essential parts of the 
mill. The number of these appliances is so great and the kinds are so 
varied that a detailed description of all of them is impossible, and since 
it would be unprofitable to describe only a few forms, little more than an 
attempt to mention some of the more important ones will be made here. 
For getting heavy material in and out of furnaces and delivering it to the 
mill, electrically operated charging and drawing machines are used. These 
machines are of two general tj^pes, namely, those that travel on overhead 
tracks and those that move on a track laid on the mill floor. For handling 
material during the rolling process, roll tables are provided for large mills, 
while various forms of appliances, called repeaters, are used on small mills. 
Roll tables consist of a frame work and a number of rolls, which may be 
rotated at will, mounted thereon. For operating these rolls, the steam 
engine has been replaced by the electric motor in all new mills and also 
in most of the old ones. Roll tables may be either stationary or movable. 
Movable tables, often used on three-high mills, may be of the tilting, the 
lifting, or the traveling type. Tilting tables are mounted on an axis of 
rotation, which may permit one or both ends, depending on the location 
of the axis, to be raised and lowered, whereas lifting tables always remain 
in horizontal positions and may be moved in up-and-down directions only. 
Traveling tables, which are now to be found only on the old mills, move 
along on tracks laid on either side of a roll train, and may be of the tilting 
type also. After the rolling, cooling beds, of which there are many types 
and forms in use, must be provided to receive the material from the mill. 
The straightening of the material, which irregularities of the rolling and 
cooling often makes necessary, is done in roll, or machine, straighteners 
or by means of gag presses. In order to keep up with the mill only the most 
rapid methods of cutting are permissible. For this purpose only two 
instrumentalities are available, namely, the saw and the shear, either of 
which may be used on hot or cold material. Shears are of three general 
types; namely, the alligator, used only for cutting light weight material; 
the guillotine, which is employed generally for all classes of work; and the 
flying shear, designed to cut billets or bars while they are in motion. The 




336 


THE ROLLING MILL 


power employed to operate the shears is hydraulic for the heavier materials, 
such as slabs and large blooms, while steam and electric power are used 
for all other work. 


SECTION III. 

SOME GENERAL FEATURES PERTAINING TO OPERATION OF THE ROLLING MILL. 

The Mill Force: Of equal importance with the equipment of a mill, 
are the men who operate it and the organization and system back of them. 
Under the general superintendent of the steel plant there may be a number 
of rolling mill superintendents, each of whom will havb charge of a group 
of mills turning out similar products. As his assistants, the mill superin¬ 
tendent selects foremen, each of whom are responsible for the successful 
operation of one or two of the mills. Below the foreman the mill is divided 
into departments, with a man at the head of each, who is charged with 
the performance of a certain part of the work. Thus, there is the heater 
who has the heating of the material to look after; the roller, who superin¬ 
tends the actual rolling process; the engineer who tends the engine, or an 
electrician, if motors are used for running the mill; and the shearmen, 
whose duty is to see that the product is properly cut. Besides these, other 
departments, such as the machine and the electric shop, the inspection and 
shipping departments, play important parts in the mill operation, though 
they do not come under the direct authority of the mill superintendent. 
When it is remembered that the failure of any one of these may close down 
the whole mill, the importance of system and of the personnel of the organi¬ 
zation is more fully appreciated. 

Duties of the Roller: So far as the product of a given mill is con¬ 
cerned, it would appear that the roller and roll designer are the chief figures. 
Co-operation between these two men is essential, for in a measure their 
interests are identical; the roll designer decides how the work is to be 
done, and the roller sees that it is done properly. The latter will, therefore, 
concentrate his attention upon the product, and with caliper, gauge, or 
templet "will take frequent measurements to make certain the material is 
being rolled true to the dimensions specified. He will keep a sharp look-out 
for underfills, overfills, fins, guide marks, collar marks, laps and any other 
rolling defects, and make the necessary adjustments to correct them. 

Fins: It is the intention to discuss the defects of materials in con¬ 
nection with the rolling of each particular class of product, but in all rolling 
where grooved rolls are used, the occurrence of fins is so liable to happen 
that it is well to consider them here, more especially since there will be 
occasion to use the term frequently. Fins are formed when the section is 
too large for the pass it is entering, or whenever, in designing the pass, 
proper allowance has not been made for the spread of the material, thus 





OPERATING FEATURES 


337 


causing the metal to flow out between the flat bodies of the rolls on each 
side of the groove. If this fin is thin and wide it will be folded over without 
welding and form a lap, when the piece, after turning, has been sent through 
the next pass. Besides, fins may be dangerous, for if the rolls are very 
close together any spreading of material between them is likely to break 
them. 

The Different Passes and Stands in mills that roll finished shapes 
are given class names. Thus the first rolls the piece enters in the mill are 
used mainly to reduce the size of the bloom or billet, and the piece generally 
leaves them in the same shape it entered. These passes are called the 
roughing rolls and the stand or stands is spoken of as the rougher, or 
roughers. If the succeeding stand merely carries this reduction further, 
it is called the pony rougher. The stands and passes in which the actual 
shaping of the piece is done are called the strands, usually numbered 1, 2, 
etc. The pass next to the last is called the planisher, but since in roll 
designing this pass may be looked upon as the first pass leading back from 
the finished section to the bloom, some designers call this pass the leader. 
The last pass is always called the finishing. 

Factors Affecting the Rolling Operation: In the rolling of steel 
there are five factors to be considered, namely, the temperature of the 
steel during the rolling, the chemical composition of the metal, the speed 
at which the rolls are revolved, the draught in each pass, and the diameter 
of the rolls. Furthermore, these factors should be considered from the 
three different standpoints of power, or energy, required to deform the 
steel; their effect upon the rolling properties of the metal, that is, the way 
it will spread, bend and flow in the rolls; and their effect on the quality of 
the finished product. All these matters have not been fully investigated, 
and our knowledge concerning them is somewhat meager, but in order to 
invite attention to these subjects, a brief summary of what is known about 
these factors is appended. 

Effects of Temperature: The influence which the working of steel at 
different temperatures may have upon the quality and properties of the 
product has already been discussed under the caption of Hot and Cold 
Working, (Chap. II, Sect. 1.). Relative to the power or energy require¬ 
ments and the rolling properties of the metal, it is to be observed that the 
higher the temperature is raised the more plastic the steel becomes. Thus, 
while, a .10 per cent, carbon steel, for example, will give a tensile strength 
of about 50000 pounds at atmospheric temperatures, at 600 °C it will break 
under a pull of 20000 to 25000 pounds per square inch, at 700 °C under a pull 
of about 11000 pounds, and at 800°C imder a pull of about 6000 pounds. 
Between 800°C and 900°C a distinct discontinuity in the tensile strength 
occurs, with the result that at 900°C the tensile strength will suddenly 
increase to nearly 9000 pounds. From this point the strength decreases 




338 


THE BOLLING MILL 


with rising temperature, being about 6500 pounds at 1000°C., about 4600 
pounds at 1100°C., about 3000 at 1200°C., and approaching zero at 1460°C., 
the fusion point. From these facts it would appear that the higher the 
temperature of the steel the easier will it be deformed. But there are other 
features that tend to keep both the initial and final working temperatures 
within certain well defined limits. Since steel assumes a semi-fluid state 
at temperatures somewhat below its fusion point, heating to within 
less than 200 °C of this point exposes it to the danger of overheating or 
so-called “burning”. For dead soft steels the initial temperature should 
not exceed 1250°C, and for high carbon steels, (1.00% to 1.20% carbon) 
this temperature should not exceed 1050°C. In order to secure the greatest 
refinement of grain, either the initial temperature or the speed of rolling 
should be adjusted so that the finishing temperature of the rolling will be 
above, but as near the critical range of the steel as possible. 


The Effect of Chemical Composition need be considered here only 
from the standpoint of energy required and rolling properties. As to the 
energy required, experiments have shown that slightly more work is 
required to roll a steel containing 1.00% carbon than for steels containing 
only .10% carbon. Whether this difference was due entirely to the lower 
temperature at which the higher carbon steel was rolled or also partly to 
the higher content of carbon could not be determined. In the hope that 
it would help to solve this question, an experiment was performed with 
the object of comparing the tensile strength of high carbon and low carbon 
steels at rolling temperatures. For this purpose three steels having a 
carbon content of .10 percent, .22 per cent, and 1.10 per cent, but otherwise 
of approximately the same composition, were selected. The results from 
pulling the first have already been given. The mechanical properties of 
the other two were compared at 900°C only. The average results obtained 
from pulling ten pieces of each under similar conditions at the initial 
temperature of 900°C are as follows: 


Carbon Content 



Tensile Strength 
13,500 lbs. 
18,800 lbs. 


Elongation 
in 8" 
110 % 

58% 


Reduction 
of Area 
94% 
83% 


These results would indicate that the higher carbon steel is somewhat less 
plastic at rolling temperatures than the lower carbon steel. Therefore, it 
would require more energy for rolling, and would not spread or elongate 
as readily as the steel of lower carbon content. As to the effect of the 
other elements in plain steel, phosphorus may produce effects similar to 
those of carbon, sulphur tends to produce red shortness, while manganese 
tends to offset the effects of sulphur and oxygen and improve the rolling 
properties. Open hearth steel, which is low in its phosphorus content, 
tends to spread more in the rolls than does Bessemer steel, which is higher 
in phosphorus. The rolling properties are still more strongly affected by 




OPERATING FEATURES 


339 


certain alloying elements, such as nickel and chromium. The difference in 
rolling properties produced by difference in chemical composition may not 
be noticable in the rolling of the simpler sections, but may cause much 
trouble in the rolling of complicated sections with wide thin flanges or legs. 
Thus, in one instance of such a complicated section, it was found that while 
the section rolled perfectly with one heat of steel, it was imperfectly formed 
when rolled from another heat in which the carbon content was ten points, 
the manganese fifteen points, and the sulphur two points higher. 

The Effect of Speed: The speed of rolling is the factor which has received 
the least attention from the viewpoint of its effect upon the material. It is 
the consensus of opinion among steel workers, however, that the speed of 
rolling undoubtedly has an influence upon the quality of the product. It is 
evident that the faster a piece of steel is deformed the less time the 
molecules have in which to adapt themselves to the deformation and the 
greater their resistance to the deformation. Consequently the stretching 
effect of the rolling, as previously explained, increases in undue proportion 
to the compression. If the speed of the rolls were increased sufficiently 
they would then have a greater tendency to slip on the piece, and the 
stretching effect would tend to become a tearing effect. However, it is 
not speed alone that produces this effect but draught and speed together. 

Draught: Draught is the difference in sectional area between one 
pass and the next succeeding one, and is usually expressed in per cent. 
While there are cases where as high as a 50% reduction occurs, and one 
case in which a 70% reduction is made in a single pass, the draught will 
seldom exceed 36%. These heavy draughts take place in the roughers, 
where most of the reduction occurs. In the strands the reduction will be 
as evenly distributed as possible, and will sometimes be as low as 10%. 
If the leader is used as a planishing pass very little reduction is effected 
there either, while very little reduction, with a few exceptions, ever occurs 
in the finishing pass. This pass being intended to give an exact finish to 
gauge and to true up the piece, it is important that very little work be done 
in it in order that it may be subjected to as little wear as possible. Since 
a piece must be finished before it has lost its heat and has cooled below the 
rolling temperature, which cooling is very rapid in the case of small sections, 
the rolls must be run at a speed that will carry the piece through the rolling 
before it has become too cold. The number of passes and the size of the 
piece to start with controls the draught. Aside from these features the 
desire to increase output acts as an incentive to increase both the speed 
and the draught to the limit the material will stand. There are many 
considerations, however, that operate to hold down both speed and draught 
below that which will do injury to the steel. One of these is the additional 
power required for very rapid reduction; another is the severe strain on the 
rolls and other machinery when the piece enters the rolls at high speed 
and with large draught. In mills composed of several stands, especially 



340 


THE ROLLING MILL 


in the case of the continuous mill, the speed of all preceding stands is deter¬ 
mined by the speed of the finishing stand. In hand mills, the speed is 
restricted to the highest velocity, about six hundred feet per minute, at 
which the catchers can grasp the piece with the tongs. The magnitude of 
the draught is restricted by the limiting angle at which the rolls will “bite’, 
the piece on entering. This angle is found, by experience, to be about 30°’ 



Fig. 54. The Limiting Angle of Rolling. 


Above this angle the resultants of the forces of compression have receded 
so far from a parallel to the line joining the centers of the rolls that they 
exert a push on the piece, and the resultant of the forces of elongation is so 
nearly vertical that the horizontally inclined component due to friction 
only is not sufficient to balance this backward push and drag the material 
between the rolls. In order to increase this limit, a series of horizontal 
and well rounded grooves, called ragging, are often cut in the surface of 
the roll, giving it the appearance of a half formed cog wheel. Since these 
grooves leave ridges in the material, they can be resorted to only in bloom¬ 
ing mills, billet mills, or roughing stands. Even then the grooves must be 
cut with considerable care in order to prevent these ridges being folded 
over into laps in succeeding passes and rolled into the material, to appear 
as seams in the finished product. 

The Effect of Diameter of Rolls: From a study of Fig. 54, it will be 
seen that the larger the roll diameters are the greater will be the draught 
that may be taken without exceeding the limiting angle of rolling. For the 
same draft, however, a large roll gives a greater roll surface area in contact 











EFFECT OF SIZE OF ROLLS 


341 


with the metal than a small one and therefore requires more pressure to 
force it into the metal, thus putting a greater tension on the housings and 
requiring more energy to drive it. The large roll gives an affect more like 
that of pressing than the small, roll, and, with the draft and speed properly 
regulated, the effects of the rolling can be made less superficial with the 
large roll. The large roll tends to cause the metal to spread more than 
the small roll. Hence, the size of the rolls is a factor to be considered in 
designing rolls for flats and other products in which the spread of the metal 
may affect the dimensions of the finished article. 



342 


PREPARATION OF STEEL 


CHAPTER IV. 

PREPARATION OF THE STEEL FOR ROLLING. 


SECTION I. 

INGOTS AND THEIR DEFECTS. 

Preparation of Ingots: In order that the large bodies of metal 
refined at one time by the various methods of steel making may be obtained 
in a convenient shape for rolling, it is necessary that these large bodies 
be divided into smaller ones, called ingots, of a uniform shape and size. 
These conditions are obtained by pouring the metal while it is still molten 
into moulds of the desired dimensions, where it may be allowed to solidify 
in part or in whole before the mould is removed. Before rolling begins, 
however, the ingot must have been allowed to solidify throughout, and the 
whole mass should be of uniform temperature. But in cooling naturally, 
these conditions are not fulfilled, because the outside of the ingot, being 
the part from which the heat is removed the most rapidly, is the first to 
solidify. With this fact in mind, it is easily understood how, in any case 
of natural cooling, the interior is the last to drop to any given temperature. 
In fact, the moulds are stripped from many ingots while the central portion 
is yet in the liquid state. This fact was early recognized by steel workers, 
and so it was originally the custom to strip the ingots as soon as possible 
and place them in a tightly covered hole or pit in the ground, where the 
heat from the interior of the ingot was slowly conveyed to the outside by 
conduction, and sufficed not only to heat up the colder exterior part of the 
ingot but also to supply heat to the pit, which, with careful manipulaton, 
was sufficient to maintain a rolling temperature. This process was called 
soaking, hence the name soaking pit. In order to bring the soaking under 
better control and make it adaptable to varying conditions, means for 
supplying additional heat was introduced, so that the modern soaking pit 
is in reality a kind of heating furnace, a detailed description of which will 
be given later. 

Ingot Defects: A prerequisite to faultlessly finished material is 
perfect ingots, and by a perfect ingot is meant one free from all cavities 
or openings and made up of material that is homogeneous throughout. 
Unfortunately, the natural laws that govern the solidification of the liquid 
metal operate against both these requirements, and develop the well known 
natural defects in ingots called piping, blow holes, segregation and crystal¬ 
lization. Added to these are other defects, both incidental and accidental, 





INGOT DEFECTS 


343 


such as checking, scabs, and slag inclusions. A brief discussion of these 
defects follows; but an understanding of their causes requires a study of the 
laws that control the cooling of ingots. 

The Nature of the Cooling of an Ingot: The ingot moulds in common 
use are tall box-like shapes made of cast iron; they are open at both ends, 
one of which is a little smaller than the other to give the mould a little 
taper; and have a square or rectangular section slightly rounded at the 
corners. In use, one end of the mould, usually the larger, is closed by 
the stool on which the mould stands in an upright position. As soon as 
the molten steel is poured into this mold, the metal next to the mold and 
stool is chilled by contact with the cold surfaces and solidifies on the bottom 
and sides to form what is called the skin of the ingot. As more and more 
heat is absorbed by the mold, this skin grows in thickness, but due to the 
increase in the temperature of the mold and the insulating effect of the 
skin, itself, it grows at a rapidly reduced rate, imtil the process becomes 
so slow that it can be considered as a normal cooling. The cooling then 
takes place by a dissipation of the heat through this skin along lines per¬ 
pendicular to the surface of the solidified shell, which acts as the conductor, 
with the result that this shell gradually grows in thickness, the growth 
progressing toward the center until all the metal is in the solid state. 
The laws of freezing which the metal obeys, combined with this manner 
of freezing, gives rise to the natural defects enumerated above. 

Pipes: One of the most noticeable effects of the freezing is the pro¬ 
duction of a more or less cone-shaped cavity at the top of the ingot, known 
as the pipe. Pipes are the result of the contraction of the metal on 
solidifying in the manner just described. This contraction amounts to 
about two-hundredths of the linear dimensions of the ingot, and if the 
manner of cooling did not set in play forces which oppose the contraction, 
no pipes would form, and a perfect ingot would measure one-fiftieth smaller 
than the mould in all its dimensions. In ordinary ingots much of 
this difference in volume is represented by the pipe. Since the skin and 
the more slowly formed walls built up by the cooling are rigid, the void 
left by contraction is filled by the metal in the central portion that 
still remains fluid, the force of gravity directing the flow downward at 
all times. After solidification of the metal is complete, further contraction on 
cooling tends to open this pipe still farther towards the bottom, because 
the exterior, being the colder, is the more rigid and is capable of 
stretching or tearing the more plastic interior. The greater portion of 
the surface of this cavity is likely to become more or less oxidized, 
and, since the oxidized portion is not welded up in the rolling, the pipe 
will appear in the smallest rod or wire into which this part of the ingot 
may be rolled. Aside from injuring material, pipes are liable to cause 
accidents in rolling, so the steel maker is very anxious to get rid of them 
as early as possible. 




344 


PREPARATION OF STEEL 



Fig 55. Split Ingots Showing Various Forms and Degrees of Pipe. 






INGOT DEFECTS 


345 


x 



Fig. 55—Continued 









346 


PREPARATION OF STEEL 


Methods of Reducing Waste due to the Pipe: Obviously, the only 
way of avoiding this pipe is by discarding the portion of the ingot affected. 
Various schemes for reducing the waste due to this cause have been and 
are being tried, and some of them are fairly successful, among which the 
most promising seems to be the so-called hot top mould. As explained 
in connection with the open hearth process, in one form of these moulds 
the ingot is cast with the smaller end down, while the larger end is sur¬ 
mounted with a short mould which is lined with refractory and non-con- 
conducting material, such as clay. This lining reduces the size of the top 
section and keeps the top of the ingot in the molten state until the ingot 
proper has solidified. Thus, the pipe is brought up into the cope, or sink 
head, which is of much smaller section than the ingot, and the waste due to 
the cropping is decreased accordingly. This ingot is stripped by first 
removing the insulated top section, gripping the sink head with tongs and 
then lifting the ingot out of the mould. In a patented form of this mould, 
known as the Gathman mould, a similar effect is produced by decreasing 
the thickness of the mould at the top. Since the heavy part of the mould 
causes a more rapid cooling than the thin portion, the metal at the top is 
the last to freeze. 

Blow Holes: In the molten state iron, or steel, is capable of dissolving 
large volumes of gases, such as oxygen, carbon-monoxide, nitrogen and 
hydrogen, this solvent power increasing with the temperature. The iron 
probably unites with all the oxygen immediately after it is dissolved, hence 
it is retained by the metal in the solid state if chemical means are not 
employed to remove it. In case of the other gases, however, no such stable 
combination takes place, and they are largely thrown out of solution just 
previous to the time when solidification of the metal occurs. As the metal 
is in a more or less plastic condition at this time, the last gases thus liber¬ 
ated may not be able to escape from the body of the metal, in which case 
they collect in bubbles, as a gas will in making its way out of any fluid. 
Each bubble will then form a small cavity in the metal which is known as 
a blow hole. These holes will vary in size from those visible through a 
microscope to large pockets, the dimensions of which can be measured in 
inches. The smallest ones are liable to occur just below the skin of the 
ingot where the rapidly cooling metal gave the tiny bubbles of evolved 
gases time neither to escape nor to collect in larger bodies. Here the gases, 
unable to escape upward on account of the very viscous nature of the 
metal, form tube-like cavities that extend at right angles to the skin wall 
of the ingot and toward the center. In the rolling of the steel, the blow 
holes are closed up and welded together provided their surfaces have not 
been oxidized, in which case they will not weld and will produce defects 
in the finished articles. Blow holes near the center of the piece, known 
as deep seated holes, are less liable to oxidation, hence are the least harm¬ 
ful. But the small blow holes beneath the skin of the ingot are liable to 
be exposed to the air, or be filled with liquid oxide of iron, in which case 




INGOT DEFECTS 


347 







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348 


PREPARATION OF STEEL 


they produce seams in the finished articles. Blow holes are an ever 
present menace. But correctives may be employed successfully, and they 
are seldom a source of serious damage in steel that has been properly 
worked in the process of manufacture and thoroughly deoxidized at the 
time of recarburizing. In this respect the use of aluminum in the mold at 
time of casting has been found to be very effective. Blow holes have the 
effect of reducing the size of the pipe, and on this account are to be de¬ 
sired if they are deep seated. Various attempts to overcome both blow 
holes and pipes mechanically by means of subjecting the metal to compre¬ 
ssion while in the molten state have been tried, but the expense of 
operating these appliances more than outweighs the good derived, 
especially since the steel discarded on account of pipe is available for use 
as scrap in the open hearth. 

Crystallization is the property possessed by iron, in common with 
many other substances, of forming crystals on solidifying. The size of 
the crystals depends on the composition of the steel and the rate of cool¬ 
ing; in general, the slower the cooling the larger the crystals will be. It 
is plain that the temperature at casting and the size and shape of the 
ingot and mold control the rate of cooling. If the crystals are large, the force 
of cohesion among the crystals is decreased by the increased area of contact 
and the larger size of their cleavage planes. The effect of unduly large 
crystals is to make ingots liable to tear in rolling. This condition is 
sometimes called ingotism. The deformation and refinement of the 
crystals in rolling prevent their effect showing up in finished product that 
has been properly worked. 

Segregation: Steel is a mixture of various compounds and elements; 
some of these are to be looked upon as impurities because of their detri¬ 
mental effects, but others are necessary to impart the properties most 
desired in the product. While in the molten state these solid ingredients, 
like the gases just mentioned, are held in solution by the iron, a power 
which it does not possess to the same degree at temperatures below its 
freezing point. Some of these ingredients freeze at a lower temperature 
than the iron. Furthermore, the solution, following the laws of selective 
freezing, undergoes a series of changes and recombinations with the formation 
of various eutectic solutions, which increase the number of substances that 
solidify normally at much lower temperatures than pure iron. With such 
an aggregate, it is easy to see how the process of solidification results in 
an isolation of the ingredients. Those substances having the highest 
melting, or freezing points, of course, are the first to crystallize. This 
separation, then, has the effect of concentrating the solution of the sub¬ 
stance having the lower freezing points in the mother liquor. This process 
continues until the mother liquor is made up only of that substance that 
has the lowest freezing point, when it, too, will freeze, forming in the ingot 
a solid mass very different in composition from the metal that crystallized 




INGOT DEFECTS 


349 


out at the beginning. Under such conditions, it is to be expected that the 
substances with the low melting points would be found in one spot or locality 
in the ingot and that this spot would be located near the top and center 
of the ingot, that is, at the bottom of the pipe, where the metal was the 
last to freeze; and to some extent, this is what actually does occur, so 
that this central position of the ingot is spoken of as the line of segregation. 
That the condition is not even more pronounced is due to the closing in, or 
entrapping, of the small pockets of the mother liquor during the freezing 
and to the high viscosity of the fluid. Like the pipe and the blow hole, 
segregation cannot be overcome, but by rapid cooling and the use of 
aluminum to quiet the metal it may be lessened somewhat. In conclusion 
it should be remarked that this is one of the fundamental reasons why 
a range in chemical and physical specifications is imperative, at least from 
the manufacturer’s point of view. 

Checking and Scabs: If the surface of a mold is very rough, or 
contains cavities, so that resistance is offered to the natural contraction 
of the steel, transverse cracks in the skin of the ingot may result. 
However, in spite of all precautions that may be taken cracks in ingots 
will occur, and a study of this matter indicates that this defect is more 
liable to occur in certain grades of steel than ir others, and particularly 
in those steels in which the carbon content is between. 17% and .24%. These 
cracks become oxidized and subsequently produce a seamy product. 
Scabby material is often caused by improper pouring. If care is not taken 
to prevent it, the metal may be splashed against the side of the cold mold 
during the pouring. These splashes tend to stick to the mold, and, 
becoming oxidized on the surface, will then appear as scabs on the ingot 
after it is stripped. These defects very often show up after rolling in the 
form of seams and slivers; in plates they will form serious surface defects. 
Such defects are entirely avoided by bottom casting the ingots. A cracked 
mold that must be forcibly drawn by the stripper may produce similar 
defects. 

Slag Inclusions: Various explanations are offered to account for the 
presence of slag particles held within steel. Slag inclusions may be due 
to an improperly finished bath, or in case the furnace practice has been 
good, they may be caused by slag being stirred into the steel and mechani¬ 
cally held by it while the heat is being poured. They may also be due 
to dirt in the ladle or molds, or they may be the result of slag forming 
reactions that occur during the deoxidation of the metal in the ladle or 
molds. The latter cause would seem most conducive to the formation 
of the minute slag particles that occur so frequently in nearly all steels. 
Slag particles if given the opportunity, will rise to the top of the metal in 
the ladle, but for lack of time small particles do not always do so. Slag 
particles remaining in steel after it has been teemed have little opportunity 
to rise, because the chilling of the steel by the mold is so rapid, and they 




350 


PREPARATION OF STEEL 










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INGOT DEFECTS 


351 






Showing the Region of Greatest Segregation. 



























352 


PREPARATION OF STEEL 


are, therefore, entrapped. Hence, deoxidation in the mold should be 
controlled by good judgment and avoided when possible. Large slag 
inclusions are an original source of blisters in finished products. 

Size and Shape of I ngots: With regard to the size of ingots a number 
of factors operate to control both the size of the section and the length. 
First of these is pouring cost. It is obvious that the cost of teeming a 
50-ton heat into two-ton ingots will be much greater than if the same heat 
is cast into four-ton ingots due to increased number of molds required, 
the increase in scrap produced, and the longer time consumed in stripping 
and charging into the soaking pits, etc. The cost of rolling may be in¬ 
creased, also, for a long ingot may be rolled with the same number of passes 
as a short one of the same section. The product desired, also, is a factor 
in determining the size and the shape of the ingot. In plate mills, for 
instance, which operate independently of slabbing mills, the size of the 
plate to be rolled determines the size of the slab ingot. The blooming 
and slabbing mills and their equipment, once installed, fix a limit to the 
size of the ingot both as to section and length. As to their shape, ingots 
may be of any convenient form, though for rolling they are usually 
square or rectangular in section with rounded corners. These forms are 
easiest on the steel, as the flat sides offer the least resistance to contraction 
on cooling and the rounded corners prevent rapid cooling along the edges, 
which would result in cracks from subsequent contraction on cooling. For 
forging large rounds, a round ingot with a corrugated surface is used. 
The corrugations permit expansion and contraction of the ingot without 
the danger of developing cracks that are liable to occur in the surface and 
interior of ingots cast in a perfectly cylindrical mould. The taper on in¬ 
gots is to facilitate the stripping. To express the size of a rectangular 
ingot the dimensions of its largest section are always given, unless other¬ 
wise specified. Thus, a 23^ inch ingot means it is 233^ inches square 
at the butt; an 183^ x 213^ inch ingot means it is rectangular in section and 
183^2 x 213^ inches at the butt. 


SECTION II. 

THE CONSTRUCTION OF THE SOAKING PIT. 

General Features of the Soaking Pit: The soaking pit of modern 
construction is so built that it can be used either as an old time pit or as a 
heating furnace. Briefly, soaking pits are deep chambers, or underground 
furnaces of square or rectangular sections, heated by the regenerative 
principle and opening at the top. As to size, they are built large enough 
to contain four, six, or eight blooming mill ingots per hole, in an upright 
position. The older furnaces contain four ingots per hole, while the capacity 
of the most recent ones is eight ingots. The increase in size is due mainly to 
the economy in fuel which is obtained by the use of large pits. While the 
details of pit construction may vary somewhat at different works, yet the 
form and principle of all are alike. Therefore, it is sufficient to study but 
one, which may serve as an example of all. For this purpose, a six ingot 
furnace at Duquesne will be described somewhat in detail. 





THE SOAKING PIT 


353 


Arrangement of the Pits: For heating the ingots for the two 
blooming mills at these works, the 38-inch and 40-inch mills, there are 11 
rows ol pits, or to be more exact, 11 furnaces of 4 holes each. The holes are 
numbered 1 to 44, inclusive, No. 1 to No. 20 and No. 37 to No. 40 serve 
the 38-inch mill; the other 16, No. 21 to No. 36, inclusive, serve the 40-inch 
mill. In case a furnace for the 40-inch mill is off for repairs No. 5 furnace, 
containing holes 17, 18, 19 and 20, may be substituted. The first nine 
furnaces are built to contain six 22" x 22" ingots per hole, but numbers 10 
and 11 are constructed to hold eight ingots per pit. This gives a pit cap¬ 
acity for the 40-inch mill of 96 ingots, and for the 38-inch mill, 184 ingots. 
The furnaces with the exception of No. 1, are built in groups of two each. 
From center to center of each two adjacent furnaces, the distance is thirty- 
three feet. 

Equipment for Handling Ingots: Spanning these soaking pit 
furnaces are electric traveling cranes, two of which are over furnaces No. 10 
and No. 11, and four are over No. 1 to No. 9, inclusive. These cranes are 
Morgan 6-ton machines, and are equipped with Westinghouse motors as 
follows: 50 h. p. on the bridge, 50 h. p. on the hoist, 10 h. p. on the 
trolley, and 5 h. p. on the tongs. The main hoist is operated by a gear 
hoist and shafting rack. The tongs are connected up with a drum on a 
lifting arm, giving a vertical movement of about nine and one-fourth feet. 
The tongs are actuated by means of a curved groove in the main hoist so 
that their distance apart may be varied. The tongs are equipped with four- 
inch bits, giving a distance between the two bits, when in the closed or 
lowered position, of sixteen inches and when in the raised or open position a 
distance of nineteen and five-eighths inches. Thus the largest ingot that can 
be gripped is one about eighteen inches at the top. When larger ingots, such 
as the 22" x 22" size, are to be handled it is necessary to remove one bit. 

Construction of the Pits: In detail the construction of a six-ingot 
soaking pit furnace is as follows: Each furnace or pit contains four rect¬ 
angular holes, eight feet long, five feet three inches wide and eight feet 
seven inches deep. These holes are built side by side in the furnace, and 
are separated only by firebrick walls. Each hole has two air regenerators, 
one on each side, so that in connection with each furnace there are 
eight regenerators. The holes are closed by firebrick covers, each cover 
being supported on four wheels which roll on cast steel rails lying on the 
division wall between the pits and fastened at their ends to the I-beams 
supporting the platform about the pits. The walls enclosing the checkers 
and those supporting the pit proper rest on a concrete foundation twelve 
inches thick. These walls are built of firebrick, faced on the outside 
with river brick. The outside walls are about eighteen feet high, and the 
river brick wall directly under the pit is about eight feet high. The top of 
this river brick wall is protected by cast iron coping plates. Placed 
vertically on these coping plates and extending up into the firebrick 
bridgewall are cast iron end plates. On the coping plates rest also the 



354 


ROLLING OF STEEL 



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Fig. 58. Cross Section Drawing of a Four-Hole Six-Ingot Soaking 
Pit Furnace 

































































































































































































THE SOAKING PIT 355 


steel I-beams supporting the cast iron pans which form the bottom of the 
pits. A pan is made in two sections with a semi-circular hole on the 
inside edge of each section, so that when they are fitted together there 
will be a circular opening about ten inches in diameter through which the 
cinder can be removed from the pit. Each section rests on three ten-inch I- 
bearns. About one foot on each end of the pan is flared upward at an angle 
of 45°. There are five cooling boxes resting on the I-beams, three inside, 
or intermediate cooling boxes, and two end ones. The inside cooling boxes 
are in the division walls between the pits, and the end ones are in the end 
walls of the two outside pits. Each of these boxes rests on two 
I-beams. The boxes are hollow, being open on the bottom, and the lower 
half of the end of the bottom is cut off at an angle of about 45°. Thus, 
these cooling boxes and pans form with the end plates a triangular space 
through which the air circulates and forms the air cooling system for the 
bridgewall. On the top of the cooling boxes and near each end, there is 
a four-inch hole, and when the walls between the pits are built up, this 
opening is extended up to the surface so that a circulation of air is main¬ 
tained through it. The boxes are cast iron, one inch thick, eight feet nine 
inches long, twenty-eight inches high and are fourteen inches wide inside 
at the bottom and four and three-fourths inches inside at the top. The 
pans are lined with nine inches of firebrick set in firebrick mortar. The 
cinder hole is built up of nine-inch side-arch brick. The pit, then, 
to above the slag line, is lined with chrome brick, as these are the only 
bricks that are not fluxed by the slag formed. Next to the coolers, however, 
there is one four and one-half inch course of firebrick, laid in fireclay, but 
on these there is a four-inch course of chrome bricks, laid dry, and at the 
front and back of the pits, at the bridge wall, this chrome brick lining is 
nine inches thick. There are, in all, seven courses of chrome bricks, which 
brings the wall even with the top of the cooling box. Above this level, 
the walls are built entirely of fire brick. The side of the bridgewall next to 
the checker chambers is capped with heavy firebrick tiles (1334 x 6 x 234") 
giving a width to the firebridge of twenty-two and one-half inches. The 
chrome bricks are heavily coated with silica slurry, which affords an 
added protection. The use of this slurry is especially important on the 
front and back, for the bridgewall is the weakest part of the furnace, 
because it is subject to the intense heat of the products of combustion 
leaving the pit and, therefore, has a tendency to crack and spall. The 
firebrick part of the walls inside of the pit are coated with a slurry of 
fire-clay. This coating fills up the cracks and forms a glaze which protects 
the bricks. 

The Air Regenerators are about six feet square in horizontal section 
and seventeen feet four inches deep. The sewer which conducts the air 
from the air valve to the two chambers on the same side and farthest from 
the stack is beneath the air sewer for the two pits nearest the stack. 1 hus, 
the regenerator chambers and, hence, the pits are fired in pairs. The bottom 





356 


PREPARATION OF STEEL 


sewer is two feet seven inches high and the arch is nine inches thick. There¬ 
fore, the regenerator chambers for the two pits, on each side, nearest the 
stack are three feet four inches less in height than the back chambers. 
Between the two regenerators on the same air flue, starting at a height of 
about five feet above the bottom of the chambers, there is an eighteen inch 
firebrick wall separating the two adjacent chambers. The two pairs of 
regenerators on the different air servers are entirely separated from each 
other. The bottoms of the chambers are separated into four spaces (four¬ 
teen and one-half inches wide) by,firebrick withe walls. These walls 
extend back into the air sewer to the air valve and provide for the even 
distribution of the air. On these withe walls there is one course of firebrick 
tiles on which the checkers rest. The withe walls are three feet seven 
inches high in the two pairs of regenerators farthest from the stack and 
two feet four inches in the other two pairs, thus making the height of the 
first mentioned checkers nine feet six and one-half inches. In the two pairs 
of chambers farthest from the stack, the checkers extend up to within 
thirty-one inches of the bridgewall and in the other two pairs to within 
eighteen inches. The top row of checker bricks are laid so that the openings 
are in the same direction that the air must take in entering the pit. The 
roof of the regenerator chamber is arched, being built of firebrick thirteen 
and one-half inches thick, but the arch over the bridgewall, for a distance 
of twenty-seven inches, is of silica brick nine inches thick and laid in silica 
slurry on top of which is a thirteen and one-half inch firebrick arch. 
Silica brick is used in this construction because it is very refractory and 
can withstand a heavy load when highly heated. The whole furnace is 
securely tied together by cast iron corner binders, tie rods, and buckstays. 
Each of the four outside corners of the furnace has a corner binder fifteen 
feet ten and one-half inches high, and the four corners directly under the 
pits have binders eight feet one inch high. These binders have a twelve 
inch flange, two inches thick, provided with lugs for the tie rods. The 
binders are connected by two inch tie rods. Along the two outside walls 
of the regenerators there is a structural steel buckstay, the ends of which 
are connected, across the furnace end, by two inch tie rods. 

The Pit Covers consist of four iron castings which are bolted together 
and are held rigid at the center by a cast iron separator. Inclosed in this 
frame is a firebrick arch. As already stated, to these castings are fastened 
the wheels on which the covers roll. To each separator is fastened a steel 
piston rod connected to the piston head in a hydraulic cylinder. These 
cylinders furnish the means by which the covers are moved. In some 
plants the covers are moved by lowering the tongs into a special box in 
the separator casting and then moving the crane in the direction desired. 
The hydraulic cylinders operate under a water pressure of 500 lbs. per 
square inch. They rest on cast iron stands fastened to the floor beams, 
and the bearings for the cylinders are placed about the center of the 
cylinders, thus making them free to rotate about this point. This con- 




THE SOAKING PIT 


357 


struction is made necessary, because, as the furnace becomes old, the 
dividing walls between the pits sink and the rails bend. Therefore, the 
connection of the piston rod and the separator has a constantly varying 
elevation due to the different elevation of the rails, and it is necessary to 
have the cylinders on a rocker so that they may follow this motion and 
constantly adjust themselves in line with the piston. The extreme stroke 
of the cover piston is nine feet nine inches. In order to make the covers 
fit nicely the tops of the pits are surrounded by floor plates of cast iron. 

Fuel and Air Valves, etc.: These pits were built to use natural gas 
for fuel, but this fuel has been replaced by coke-oven gas. When natural 
gas was used for heating the pits, it was admitted through the roof of the 
regenerator chamber by means of two three-fourth inch pipes twenty-one 
inches long. These pipes were placed at such an angle (about four and one- 
half inches of slope per foot) and distance from the pit that the flame did 
not play directly on the face of the ingot, and a reducing atmosphere could 
be maintained inside the pit. The pipes, or burners, were twenty-one 
inches apart and were fed from a one and one-fourth inch pipe which in turn 
was connected up to a four inch gas manifold supplying the gas to the four 
chambers on a particular side. For coke oven gas it was thought it would 
be necessary to modify this scheme of firing somewhat in order to make 
the conditions suit the difference in the heating properties of these gases, 
but trial runs indicate that satisfactory results are obtained if the coke 
oven gas is burned in the same manner as the natural gas. For reversing 
the direction of the air there are two thirty-inch Ahlen sliding valves, and 
for reversing the direction of the gas a three-way valve. Each set of valves 
consists of two cast iron bed plates, two cast iron sliding plates, two 
hydraulic cylinders, and two hoods. The distance from center to center 
of the hoods is five feet three and one-half inches. The bed plates are 
bolted together and the cylinders are bolted to them. Each of these bed 
plates has three openings connected to flues, of which the two outside ones 
lead to the regenerators and the center one to the stack. These flues are 
twenty-two inches wide, the division walls being nine inches thick and the 
wall between the two sets of valves twenty-two and one-half inches thick. 
As to the sliding plates they are also bolted together and the two are then 
connected directly to the piston of .the hydraulic cylinder. The total 
length of the sliding plate is eleven feet one inch. Each plate has six open¬ 
ings, two pairs of which are used as air dampers, while the other two form, 
with the hood, a part of the flue to the stack. The hood rests on the sliding 
plate, and both the hood and the sliding plate are water cooled. The 
hydraulic cylinder has a stroke of two feet seven inches and a plunger 
diameter of six inches. 

Stack=Flues and Stack: The flues leading from the valve to the 
stack are three feet eleven inches high and twenty-two inches wide. In 
these flues are the stack dampers. These dampers are hand operated by 
means of a chain and a counter-weight. They slide in a guide frame made 






358 


PREPARATION OF STEEL 


in the form of a casting set in the brick work. The stacks are one hundred 
three feet eight inches high, and consist of a riveted steel shell and a lining 
of brick work. The plates of which the shell is made are one-fourth inch 
thick at the bottom of the stack and one-eighth inch at the top. The 
outside diameters of the shell at the top and bottom are respectively four 
feet six inches and five feet ten inches. The lining consists of a four and 
one-half inch course of firebrick. 

The Course of the Gases Through the Pits: Of the two thirty-inch 
air valves, the one nearest to the pits is for the two front pits and the other 
for the two back pits. Thus, for the two front pits, the air enters the inside 
valve through the top sewer, goes through the two front regenerator 
chambers, the two front pits, down through the opposite checkers, through 
the top sewer, through the inside reversing valve, then past the right hand 
stack damper to the stack. For controlling the sliding valve so that the 
two hoods work in unison, a double-acting Critchlow valve is provided. 
Each of the sliding plates is provided with two air dampers so that it is 
impossible to shut off the air from the two adjacent pits with the valves 
in either position. The gas on all four pits is reversed by one three-way 
valve, but on each side of this valve there are four other valves, so that 
the gas can be shut off separately on any pit. To reverse the direction of 
the gas and air, the gas is shut off, then the air reversed, and after it the gas 
is reversed. 

Eight Ingot Pits: The main difference between the six ingot and the 
eight ingot pits, aside from increased dimensions, lies in the fact that the 
air regenerators are provided with a special division wall. This wall is 
built parallel to the end of the pit and extends to the top of the checkers, 
the object being to retain any cinder running over from the pit in the first 
few checker openings, thus preventing the choking of all but a few of the 
checker spaces, and maintaining a higher efficiency of the regenerators. 
Also, these pits are provided with two cinder holes instead of one as for 
the six ingot holes. The furnaces are spaced forty-one feet four inches from 
center to center, and the holes are five feet three inches wide and ten feet 
seven inches long, and are spaced eight feet three inches from center to 
center. The covers on these pits can be separated about two-thirds of the 
distance from the back. On these covers the piston is connected to the 
end casting of the cover frame instead of to the separator, and there is a 
separator on each portion of the cover. When closed, the separators fit 
together and are fastened thus with hooks. With this arrangement it is 
possible to move the entire cover or, by unhooking, the back portion only 
may be moved. 

Making Up the Bottom of the Pit: Bottom making is done by a 
group of men called the bottom-makers, who are provided with shovels, 
long handled pokers and cutters. To clean out a pit, the pit cover is pulled 
back slightly, and a shield is drawn up over the front of the pit. The cinder 
hole in the bottom of the pit is then opened with the poker, and by means 




SOAKING INGOTS 


359 


of the cutters the cinder is shoved out through this hole. After the cinder 
has been removed, a piece of iron sheeting is put over the hole, and then 
the process of making bottom is begun. Coke breeze from the blast furnace 
coke bins is used to make up the bottom. Coke breeze is used because 
it absorbs and makes fragile the molten oxide that runs off the ingot, pro¬ 
tects the brick work, and helps to maintain a reducing atmosphere in the 
furnace. The depth of the coke on the bottom should be maintained at 
about eighteen inches. To provide the desired depth, making up for the 
coke and cinder that are pushed out each time, requires for each bottom 
six to eight wheelbarrow loads of breeze, which weighs about 250 pounds 
per barrow load, for the six ingot pits; for the eight ingot pits ten to twelve 
wheelbarrow loads, or about 2500 poimds, is required. This coke is thrown 
in from the front, the ends being made up first, the sides next, and lastly 
the center. The bottom is made up so that there will be two troughs into 
which the ingots may be placed. The object in providing these troughs 
is to keep the ingots away from the walls so that they will have a better 
chance to heat but at the same time will not be placed so near the center 
that they will be hit directly by the flame. During the time that the 
bottoms are being made up, the gas and air are shut off, and the stack is 
made to draw air through the cover opening so that the heat is drawn away 
from the men. Before charging ingots on a new bottom, the coke breeze 
should be allowed to become well heated throughout, as a cold bottom in 
the pit allows the butts of the ingots to remain cold, and when ingots are 
put through the mills in this condition they are liable to break the rolls. 


SECTION III. 

SOAKING THE INGOTS FOR ROLLING. 

Charging the Ingots: Ingots should always be charged into the 
soaking pits in an upright position, which explains the peculiar construction 
of the pits. There are two reasons for this method of charging. First, 
the best practice for the care of ingots demands that they be stripped as 
soon as possible after pouring and delivered to the soaking pits before they 
lose much of their original heat, because the hotter they are charged the 
quicker will they reach the rolling temperature, and little fuel for reheating 
will be required. In pursuance of this practice, most ingots, except high 
carbon, high sulphur and alloy steels, which are allowed to become solid 
throughout before stripping, reach the pits while their central portions 
are still molten and must, therefore, stand in an upright position until this 
portion has become solid, as otherwise the extent of the pipe might be in¬ 
creased and its. position would be changed. Second, by charging ingots 
vertically more surface for ingress and egress of heat is exposed to the 
atmosphere of the furnace, thus causing them to come to a uniform rolling 
temperature much quicker than would be the case if they were placed in 
any other way. 




360 


PREPARATION OF STEEL 


Heating the Ingots: From what has been said, it is easy to surmise 
that great injury can be done in the heating of the ingots. This injury 
consists of under-heating, over-heating, uneven heating, or worse than all, 
burning. Of these, under-heating and over-heating are the least harmful 
to the steel; the former increases the power required for rolling and decreases 
the time permissible for the rolling; the latter, by increasing the grain 
size and lessening the force of cohesion, makes the steel tender and liable 
to crack. Uneven heating increases the difficulties of rolling very much. 
A cold butt of an ingot, for example, may cause a roll to be broken. Burning 
may range from extreme over-heating to a temperature just below the 
melting point, where the more fusible constituents melt and run out of the 
ingot, forming cavities that, on rolling, result in defects that will be cause 
for rejection of the material. In the case of thin skinned ingots, severe over¬ 
heating may have a like result by exposing the blow holes. Besides these 
general precautions, different conditions and different grades of steel require 
different treatment. As an example of the point in question a summary 
of the soaking practice as carried out at Duquesne is given herewith. 

Week=End Charges: If hot steel is charged Saturday evening just 
before the mill shuts down, it will be allowed to soak until one or two 
o’clock Sunday morning, when gas will be admitted for about an hour. 
Soaking will then be continued until the day turn comes out at seven o’clock 
a. m. But if cold steel should be charged before the week-end shut-down, 
gas is admitted for three or four hours, the flame being reversed at intervals 
of from one-half to one hour; and the steel is then allowed to soak until 
Sunday morning. During the soaking, the stack and air dampers are kept 
closed. 

Soaking Hot and Cold Ingots: To bring hot steel to the required 
rolling temperature requires approximately the same amount of time as 
the interval between the time the heat was tapped and the time it was 
charged into the pits. Hot special steel of medium carbon content must 
be in the pits about one and one-half hours and spring steel about one hour. 
Thus, the period, from the time the heat is tapped at the open hearth until it 
can be rolled, is about three hours for Duquesne special, about two hours 
for spring steel, and one and a half hours for ordinary steel. To heat six 
cold soft steel ingots in the 6-ingot pits requires about six hours. For 
about four hours after the pits are charged, the gas and air may be admitted 
on each side alternately for half hour periods. The period of reversal 
should then be cut to fifteen minutes. Towards the last, as the temperature 
of the steel approaches the rolling temperature, the period of reversal may 
be cut to five or ten minutes, for the more frequent the reversal the more 
even will be the temperature of the pits. Cold steel is very rarely 
charged in the ingot pits, the practice being followed only after a 
shut-down when the mills start operating at the same time as the open 
hearth, for at such a time there is no hot steel on hand. The period 
required for heating cold steel in the eight ingot pits is about eight hours. 



SOAKING INGOTS 


361 


Soft steel is heated, to a temperature of about 1200° C. (2200° F.) With 
both high and low carbon steels, should only four or five ingots be charged 
in the smaller pits, the period required for heating would be greatly reduced. 
This is true especially for the low carbon steel, for with only four ingots 
to a pit it is possible to prepare the cold steel in four hours. By charging 
only six ingots in the large pits, the period may be reduced to about six 
hours. Before a cold high carbon heat (.70% carbon or over) is charged, 
the pits should be cooled for about a half hour, for if these ingots are heated 
rapidly they are liable to crack. After the pits have been cooled, the ingots 
are charged, and sometimes the covers are left open for a half hour, so 
that the steel will be heated very slowly. The period between reversals 
should not be as long as for low carbon cold steel, and so at first the reversals 
for steel of this grade are made at intervals of a half hour or less, and during 
the balance of the time the period between the reversals is about ten minutes. 
The rolling temperature of spring steel is about 1090° C. (2000° F.) 

Soaking Hot Spring Steel: This grade of steel is charged in a hot 
pit. The gas may be admitted for a half hour, the flue being reversed every 
five or ten minutes; the steel should then be allowed to soak for fifteen 
minutes, and then gas should be admitted for about fifteen minutes to bring 
up the temperature of the outside of the ingot. This steel should be ready 
to roll in about an hour. While the steel is soaking, in addition to shutting 
off the gas, it is best to shut off the air supply, also, for the effect of the 
hot air on the ingot is to oxidize or even to burn it. If the steel is very 
hot when charged, it should be allowed to soak for a half hour before gas 
is admitted; then gas and air should be admitted for about a half hour, 
with reversals every five or ten minutes. The steel should then be soaked 
for a half hour without air, and then, just before drawing, the temperature 
of the outer part of the ingot should be brought up by admission of gas 
and air again. 

Soaking Low Carbon Hot Steel: Hot low carbon steel ingots may 
be heated without danger for a half hour, the direction of the gas and air 
being reversed every fifteen minutes. The steel should then be allowed to 
soak for fifteen minutes, and before drawing the outside temperature should 
be raised. Since there is not as much danger of burning this steel as there 
is with the high carbon grades, it is not always necessary to close the air 
dampers during the time the steel is soaking. 

Soaking Medium Steels: The practice with respect to medium steels, 
.30% to .60% carbon, is to heat the ingots to about the same temperature 
as for low carbon steel. The steel, if charged hot, should be ready to roll 
in one hour after charging. 

Soaking Screw Stock: High sulphur steel is charged as quickly as 
possible after stripping. The time required to heat it is about one and a 
half hours. The steel is heated to dripping, that is, until the scale melts 
and flows readily from the surface, and is rolled when in that condition. 
Owing to the high sulphur content, it is necessary, to maintain good practice 




362 


PREPARATION OF STEEL 


in rolling, to heat it very hot, so that the steel will be very plastic. This 
condition is obtained only at a very high temperature, about 1240° :C. 
(2240° F.). Since these screw stock ingots are heated until they are dripping 
a large amount of liquid cinder is always formed, so that it is necessary 
to add a little coke in the pits after every heat of this kind to absorb this 
cinder. F 

Soaking Alloy Steels: Nickel steel is heated to about the same 
temperature as spring steel, 1090° C. Chrome vanadium is heated to about 
1250° C. Copper steel is heated according to its carbon content in much 
the same way as carbon steels. 

Drawing the Ingots: The craneman draws the ingots from the pits 
according to the orders of the heater. Usually, a definite order is followed; 
at Duquesne the regular method is to draw the two front ingots from each 
of two holes, then the two middle ones from each of the two holes, and then 
the two back ones from each of the two holes. The operation is then repeated 
on the next two holes. However, the operation may be varied; the two 
front ones in each of four holes may be drawn, thus affording more time for 
the middle ingots to heat while the others are being drawn. To transfer 
the ingots from the pits to the blooming mill tables three pot cars, two of 
which are extras, are provided. These cars are operated by 19 h. p. 
Westinghouse motors. At the 38-inch mill they are controlled and dumped 
by the manipulator man of the mill, but on the 40-inch mill, the man that 
operates the pit covers controls the movement of the car. When the car 
receives an ingot it is run to the first table roller, and there the car is tipped, 
when the ingot falls upon the table. 

Heat Balance of Pits: That the soaking of ingots is an expensive 
process is evident from the equipment required. The Gost of the up-keep 
of this apparatus is high, and the efficiency is very low, even on up-to-date 
furnaces, as the following heat balances as determined by experiment on 
some Duquesne furnaces using natural gas will show: 

Table 50. Data Relative to the Efficiency of Soaking Pit Furnaces. 

Sensible Heat in Steel Charged. 619,701 B. t. u. 

Heat of Combustion of the Gas.781,808 

Heat Carried in by Regenerated Air. 384,970 


TOTAL 


1,786,479 


Heat in Steel when Drawn. 

Heat in Gases Entering Stack. 

Heat Given up to Regenerators. 

Radiation and Unaccounted for Losses 


173,862 

386,329 

452,691 


773,597 B. t. u. 


1,786,479 


Pit Efficiencv= 


Heat Absorbed by Steel 



Total Heat Delivered to Furnace 















DISPOSITION OF INGOTS 


363 


Disposition of Ingot Products: Since the ingot is the starting point 
for all mechanical working, it is interesting to trace the material through 
the various processes that the steel undergoes to produce the many articles 
in which it is used. For this purpose the following table has been prepared, 
and requires little by way of explanation. Each dash marks a reheating 
of the material, while each word means a mill, or a set of mills, where 
work is done to produce the article named. 


Table 51. Disposition of Steel from Ingots. 

Universal Mill Plate. 

Armor Plate. 

Bloom, Sheet Bar—Sheets. 

Shaped Bloom, Large Shapes. 

[Universal Mill Plates. 

Slabs—“I Eye Bars. 

[Sheared Plates. 

Rods. 

Bars. 

Bloom, Billet —\ Bands. 

Hoop. 

Small Shapes. 

Rods. 

Ingots— Small Shapes. 

Billet—{ Bars. 

Bands. 

Seamless Tube. 

\ 

Sheet Bar—Sheet. 

Structural Shapes. 

Rails. 

Rail Joints. 

f Tube. 

[Pipe. 


Rectangular Bloom— 


Skelp— 


Forgings. 

[ Wheels. 

Cylindrical Blooms-—<| Circular Shapes. 


Shell. 


Large Forgings. 













364 


THE ROLLING OF STEEL 


\ 



i 






CHAPTER V. 

THE ROLLING OF STEEL—BLOOMS AND SLABS. 

SECTION I. 

INTRODUCTORY. 

Outline of the Plan of Study: Rolling mills are somewhat like 
houses. Thus, while they are alike as to gross features, they differ greatly 
as to details of construction. Just as the architect will strive to impart 
individuality to a building, so the rolling mill engineer and builder will 
endeavor to introduce new ideas looking to greater improvements in con¬ 
struction; and just as it is desirable to adapt a building to its location and 
surroundings, so is it found necessary to alter the details of mill construction 
to suit the conditions, local and otherwise. The result of all these influences 
on mill construction has been to produce such a variation in mills that 
there are no two mills exactly alike. Evidently, to describe all the details 
of mills and their operations is well nigh an endless task; yet it is desirable 
that the reader be given an opportunity to become so well acquainted with 
the rolling of each product that he will be more or less familiar with the 
more essential details of its production and thoroughly understand the 
conditions under which it is produced. The plan decided upon as best 
to pursue is this: An attempt will be made to describe the rolling of as 
many products as possible, and in doing so the order followed will be 
from the rolling of material from ingots, to semi-finished products, to 
finished products, as indicated in the previous diagram. In this con¬ 
nection one mill rolling the material in question will be described, as well 
as the operation in detail; after which the product itself will receive special 
attention. In describing mills, the details of one mill of each type or class 
will be given. As a sort of working outline of the plan, the following classi¬ 
fication of mills will give an idea of the ground to be covered and the 
order in which the subjects are to be treated. The general discussion 
preceding this part of the study should supply information to fill in any 
gaps that may occur in the studies to follow. 






BLOOMS AND SLABS 


365 


Table 52. Classification of Mills. 

A. Mills Rolling Material from Ingots. 

1. Semi-finishing Mills: 

a. Blooming (Cogging) Mills. 

b. Slabbing Mills. 

2. Finishing: 

a. Universal Plate Mills. 

B. Mills Rolling Material from Blooms and Slabs. 

1. Semi-finishing: 

a. Billet Mills. 

b. Sheet Bar. 

c. Skelp. 

2. Finishing: 

a. Plate Mills: 

i. Sheared. 

ii. Universal. 

b. Rail Mills. 

c. Structural Shape Mills. 

d. Wheel Mills—Schoen Mill. 

e. Wheel and Circular Shape Mills. 

\ 

C. Mills Rolling Material from Billets. 

1. Merchant Mills. 

a. Guide Mills. 

b. Bar Mills. 

c. Hoop or Strip Mills, etc. 

Blooms, Slabs and Billets: As a preliminary step toward forming 
steel into the various sections which its many uses require, the heavy 
ingots, except in certain plate mills and some large shape mills, are first 
roughly reduced, in mills especially designed for the purpose, to much lighter 
but still very simple sections, as the round, the square and the rectangle. 
When the ingot has been reduced to the dimensions of a square between 
one and one-fourth inches and six inches it is cut into convenient lengths, 
called billets; if these pieces are six inches square or larger, they are known 
as blooms: and if reduced to rectangular forms but with widths which are 
less than twice the thickness and within the dimensions specified for the 
square, the same names apply. But if the width far exceeds the thickness; 
of the rectangular section, then it is called a slab. If the output of the mill 
is mainly blooms, it is called a blooming mill in the United States or a 
cogging mill in England; if billets, a billet mill; and if slabs, a slabbing mill.. 
The blooming and slabbing are the largest and strongest mills used to roll 
steel, if the mills that roll heavy armor, of which there are no longer any 
in this country, be excepted. The reasons for the existence of these mills 
are evident. 




366 


THE BOLLING OF STEEL 


SECTION II. 

SOME GENERAL FEATURES PERTAINING TO BLOOMING MILLS. 

Size of Blooming Mills: The size of blooming mills is popularly 
supposed to be based on the diameter of the rolls, or on the distance from 
center to center of the rolls. Both these quantities are constantly changing, 
due to the wearing of the rolls, which affects their diameters, and to the 
fact that they are adjustable. The size is, therefore, based on the distance 
from center to center of the pinions, which corresponds to the distance 
from center to center of the rolls and also to their diameters, and is always 
constant. The blooming mills in use at the present time will range in size 
from twenty-eight to forty-six inches. The older mills are the smaller, 
because it was formerly the practice to cast the ingots much smaller than 
at present, and large mills were not required. The size of ingots having been 
gradually increased for the reasons already pointed out, the size of the 
mills designed to roll them were necessarily increased also. This size seems 
now to have approached a standard, and most mills of recent construction 
have rolls in the neighborhood of forty inches in diameter. 

Blooming Mills, Their Advantages and Disadvantages: Bloom¬ 
ing mills are of three general types, namely, reversing, continuous,both 
of which are two=high, and three=high. Of these, two-high reversing and 
three-high mills are the most common. As an example of the continuous 
blooming mill, the billet mill at Gary, Ind., is cited. It consists of nine 
stands of rolls arranged in tandem and separately driven by electric motors. 
Since its blooms are delivered directly to a continuous billet mill, the 
reduction of the ingot to billets is made in one continuous operation. The 
chief advantage in this arrangement is an extraordinarily large output. 
As to reversing and three-high bloomers, each of these types has its 
advantages and disadvantages, some of which it may be of interest to 
enumerate here. The main advantage of the reversing mill over the three- 
high lies in its greater flexibility. Thus, the top roll being adjustable, 
various sizes of blooms, billets or slabs can be rolled on one set of rolls, and 
the draught can be regulated to suit steel at different temperatures and of 
different grades. Even different methods of reducing the ingot may be 
employed with the same rolls. On long lengths the two-high mill is to be 
preferred on account of the greater ease with which such material can be 
handled, while the simplicity of the roll design is also a factor in favor of 
these mills. On the other hand, a reversing mill is a much more expensive 
mill than a three-high mill. In the first place the tonnage is much lower. 
On two-high forty inch mills the average output is about 2000 tons per 
twenty-four hour day, to produce which about 2500 tons of ingots are 
required, while a three-high mill of the same size will roll almost twice as 
much steel. Again, the power equipment of the reversing mill is costly 
and the loss of power is great. Reliable tests show that the total power 





BLOOMS 


367 


\ 



v 


Fig. 59. Longitudinal Section Through Rolls and Pinions of a 40" Mill. 

















































































































































































































































































368 


THE ROLLING OF STEEL 


developed by a reversing mill engine is distributed about as follows:— 

27% used in overcoming idle friction of the engine parts. 

9% used in overcoming pinion and spindle friction. 

13% used in overcoming roll journal friction. 

21% used in overcoming the acceleration of the parts in reversing. 

30% used in actually deforming the steel. 

In three-high mills where the rotation is in one direction only, there 
is no acceleration loss, besides, by the use of a flywheel, lighter engines 
than those used on the reversing mill may be used to do the same work. 
Efficiency tests on three-high mills show that about 85% of the total power 
developed by the engine is used in driving the mill, and the idle friction 
of the mill parts is about 15%, thus leaving nearly 70% of the motive 
power developed available for deforming the steel. 

Drive for Reversing Mills: Since the lengths dealt with on blooming 
mills are relatively short, the speed of the rolling is slow, but as the 
material is heavy and the pull is great, though the draughts are only 
moderately heavy, great power is required. Hence, most of the older 
reversing blooming mills are indirectly driven, that is, they are connected 
to the engine through large gears which enable the engine to travel at a 
higher speed than the mill. The power is thus multiplied by a number 
equal to the speed ratio. This speed ratio will vary in the different mills 
from as high as three to one to as low as one to one, while many mills, of 
which the thirty-eight inch bloomer at Homestead and the forty inch 
mills at Clairton and Duquesne are examples, are direct driven. A few 
reversing mills installed since 1914 are driven by reversing electric motors. 
These motor installations are very complicated. They consist of a main 
motor and a motor-generator set, which prevents the acceleration loss 
peculiar to the steam driven reversing mill and raises the efficiency of the 
mill considerably. 

SECTION III. 

AN EXAMPLE OF REVERSING MILLS—THE 40" MILL AT DUQUESNE. 

The Engine for this mill, which is driven direct, is of the twin tandem 
compound condensing type, but is operated non-condensing. It was made 
by Mackintosh-Hemphill & Co. Its size is 44 // x 70" x 60" and its maxi¬ 
mum horse power is rated at 20,000. The maximum torque at the circum¬ 
ference of a thirty inch roll is 465,000 inch-pounds. The engine may run at 
any speed up to 140 r. p. m., but the maximum speed during rolling is about 
130 r. p. m. The exhaust steam is discharged into a feed water heater. 
The throttle is controlled from the pulpit located about thirty feet in front 
of the rolls and directly over the roll tables. 

Driving Connections: A cast nickel-steel crab of six pods is keyed 
onto the crankshaft of the engine; it is four feet five inches in diameter. 
Over it, and held in place by wooden stretcher blocks is fitted the large 
end of a cast nickel steel compound coupling box, which, at this end, is 
three feet two inches in diameter. The driving spindle from this coupling 



TWO-HIGIl BLOOMING MILL 


369 


is five feet eleven and one-fourth inches long and is supported by a cast 
steel coupling carrier resting at its four corners on standard spiral car 
springs of 12500 pounds capacity, which stand eight and one-fourth inches 
high when free, seven and one-fourth inches at 4700 pounds load, and six 
and nine-sixteenth inches when fully compressed. The springs in turn rest 
on cast steel seats bolted to special cast iron shoes which are anchored to 
the shoes carrying the pinions and housings. The carriers are lined with 
one inch of babbitt metal. The mill end coupling box is two feet four and 
one-half inches in diameter and is cast to fit over the four pods Of the engine- 
end wobbler of the bottom mill pinion. 

Pinions and Pinion Housings: The pinions are of the staggered 
straight tooth type and are made of nickel steel, approximately of a com¬ 
position as shown by the following analysis: Carbon, .29%; manganese, 
.66%; phosphorus, .020%; sulphur, .030%; and nickel, 2.97%. Their average 
life is 253,575 tons of steel rolled. The top and bottom pinions are similar 
and hence interchangeable. Each one is ten feet six inches long over all 
and four feet ten inches between the necks, which are twenty-one inches in 
diameter. This diameter is further reduced to twenty and one-half inches 
at the wobblers. Tphe pitch diameter is forty inches, and the number of 
teeth is fourteen. The pinions run in solid cast steel babbitted bearings, 
the bottom of which are beveled to fit on the sills of the window of the 
cast iron pinion housings. The pinion housings are bolted to the mill shoes, 
are nine feet six inches high, and have windows 2' 7wide by 7' 6h£" 
deep; the windows are lined with one and one-fourth inch forged steel 
liners held in place by stud-bolts through the housings. A cast steel housing 
cap, to which is attached the hydraulic cylinder used for lowering the top 
roll of the mill, is fastened over the housings by means of key bolts. The 
bearings are each two feet six inches wade and twenty inches from 
front to back and may be adjusted by set pins reaching through the housings. 
The top bearings rest directly on top of the bottom bearings unless plate 
liners are used in between them to get the proper pitch for the teeth. The 
bearings are held down tight by keying the cap on tight and using liners 
between it and the top bearing if necessary. 

Spindles and Coupling Boxes: Over the mill-end wobblers of the 
pinions are fitted cast steel coupling-boxes uniting the wobblers with the 
spindles. The coupling boxes, of cast steel, are two feet six inches in diam¬ 
eter and twenty-two and one-half inches wide, and cast to fit over the four 
pods of the spindles. The bottom and top spindles are each ten feet long 
and twenty-one inches in diameter where they rest on their carriers. The 
bottom spindle is provided with wobblers twenty and one-half inches in 
diameter and two feet in length, and is nineteen inches in diameter at the 
center between the two carrier bearings. On the top spindle the wobblers 
are nineteen inches in diameter, thirteen and seven-eighths inches long and 
are curved at the ends to permit the mill end to ride up or down with the 
top roll. Twenty-three inches at the center of the top spindle is turned 




370 


THE ROLLING OF STEEL 


smooth to a diameter of twenty-one inches to give a bearing for the spindle 
carrier, which is movable. The bottom spindle rests at two points near 
its ends on two stationary spindle carriers bolted to the mill shoes. The 
carrier for the top, or vibrating, spindle consists of a cradle formed by two 
cast steel arms hung at their engine ends from two supporting rods pivoted 
on spring-supported bolts which pass through supporting brackets bolted to 
the pinion housings. In the center of the carrier is a rest for the spindle, 
and on its mill end the carrier is supported by the carrier bearing for the 
top roll, being fastened to this bearing by a forged steel pin. A coupling- 
box similar to those used with the pinions fastens the bottom spindle to 
the bottom roll; seven-eighths of an inch clearance is allowed at each con¬ 
nection between spindle and pinion or roll, respectively. For the top 
pinion, a light coupling box is used in order that it may act as a safety for 
the mill by breaking under excessive strain before any other part of the 
mill is damaged. This box is twenty-two and one-half inches in width, 
twenty-five and three-fourths inches in outside diameter, and two and one- 
quarter inches in thickness at the thinnest point. The other boxes are 
four inches thick. All coupling boxes are held in place by iron or wooden 
stretcher blocks fastened in place by steel or leather straps. 

Roll Housings: The roll housing on the engine side of the mill is set 
with its center-line fourteen feet six and one-quarter inches from the center 
line of the mill-end pinion housing, a cast iron separator and steel bolt 
holding these two housings in line. This housing is cast steel but in other 
respects is the same as the outside housing, which is made of cast iron. 
Both are bolted to the mill shoes and stand twelve feet three inches high 
above them; they are set with their center lines seven feet eleven inches 
apart and are held in line by two cast iron separators and steel bolts, one 
at the front and one at the back. Besides the mill rolls the housings also 
support four feed rollers, two on each side of the rolls, sixteen inches in 
diameter and five feet ten and one-eighth inches long. The windows of the 
housings are three feet five and one-half inches wide, nine feet deep, and 
begin two feet ten inches below the top of the housing. In the top of each 
housing is left a hole for the housing nut, which is made of brass. Through 
these nuts the housing screws for adjusting the top roll are inserted. The 
nuts are larger at the bottom than at the top; they are twenty inches in 
diameter at bottom, sixteen inches at top, and thirty-four inches high. 
They are shrunk into the housings, and over them are fastened small caps, 
twenty-seven inches high, on which the screw pinions rest. The housing 
screws, the bottom ends of which press directly down on the screw brasses 
in the cast iron breaker blocks on the rider bearing boxes of the top roll, 
are made of .60% carbon open hearth steel, eight feet three inches long and ten 
inches in diameter; the threads have a pitch of two inches. They must 
allow a lift of twenty-five inches. These screws are provided with octagon 
heads. Fitted about the heads are steel pinions which rest on the top of 
the screw caps. The pinions have a pitch of two and one-quarter inches, 
a pitch diameter of fifteen and eighty-two-hundredths inches, a face of 




TWO-HIGH BLOOMING MILL 


371 


eight inches, and twenty-two teeth. The pinions are operated through a 
gear mounted on a spider which has a pitch diameter of eighty-three and 
nine-hundredths inches, a pitch of two and one-fourth inches, a face of seven 
inches, and one hundred sixteen teeth, and is, in turn, operated by means 
of a pinion fastened to its shaft. This latter pinion has a pitch diameter 
of twelve and fifty-four-hundredths inches, a pitch of three inches, 
a face of ten inches, and thirteen teeth, and is operated by a rack with a 
three inch pitch and a ten inch face. This rack is connected up to the 
hydraulic cylinder located on the top of the pinion housing. Attached to 
the rack is the finger, which, moving over a gauge, provides an indicator 
for the size of the pass. The screws of the mill are required to lift twenty- 
five inches, but a ten foot stroke of the rack will give the screws a vertical 
movement of twentj'-eight and one-half inches, the extra length of stroke 
allowing for the wear of the roll necks and bearings. In rolling, this gauge 
can be set to give correct readings on one pass only, and to gauge the other 
passes it is necessary to add or subtract a certain quantity from the gauge 
reading. A cast iron bridge is bolted to the top of the housing and 
serves both to support the spider and to keep the housings properly 
spaced. The housings are further supported and kept in line at the top by 
two cast iron separators and two steel bolts. 

Rolls: The top and bottom rolls in this mill are alike; there are two 
in a set, and each roll weighs 26,000 pounds. A typical analysis of the rolls 
gives the following results: .61% carbon, .75% manganese, .010% phos¬ 
phorus, .030% sulphur. Their dimensions are: Total length, twelve feet 
ten inches; length of body, six feet; diameter of wobbler, twenty and one- 
half inches; diameter of necks, twenty-two inches; diameter of collars, 
thirty-three and one-eighth inches. They have five passes, the widths and 
diameters of which are 24"x31^", 12" x 29 Yz", 8" x29%", 6"x29^", 
4" x 29%". The rolls are ragged only in the twelve inch and eight inch 
passes, and here the ragging is only one-sixteenth of an inch deep; all passes 
are roughened slightly with knurling wheels. These rolls are changed every 
week and dressed in the roll shop. About three-sixteenths of an inch is 
taken off each time they are dressed, and when the collars have been cut 
down to thirty and one-half inches, the rolls are scrapped. Four sets are 
kept on hand, and one set is used once in four weeks, giving a life of about 
one year per set. The average tonnage is 82,650 tons for each set of rolls. 

Roll Bearings: The bottom roll rests with each neck on a babbitt 
lined cast steel bearing, two feet six inches wide, twenty-one and three- 
fourths inches from front to back, and six and three-fourths inches thick at 
the base; its bottom is made to fit the sill of the window, and its top is cut 
out at a twelve inch radius with one and one-quarter inches of babbitt to 
fit the neck of the bottom roll. Sheet steel shields are placed over the 
necks of the bottom roll to keep scale from getting between the necks and 
bearings. The top roll is carried in two cast steel carrier bearings, which 
in turn are supported each by two three and one-half inch square steelyard 





THE ROLLING OF STEEL 


372 


rods. These rods are mounted in sockets hung from counterweighted arms 
underneath the mill, the rods coming up through the housings and bottom 
bearings on each side of the necks of the bottom roll. The carrier bearings 
are three feet three inches wide, twenty-three and three-fourths inches from 
front to back and are six inches thick at the base. They are flat on the 
bottom and concave at the top with a twelve inch radius and babbitt metal 
one and one-fourth inches thick. On the engine side of the inner bearings 
are two lugs for receiving the pin to hold up the spindle carrier. The rider 
bearing of the top roll is cast steel two feet two and one-half inches wide, 
twenty-one and three-fourths inches from front to back, and two and one- 
fourth inches thick, with one inch of babbitt metal. It is concave below 
at a radius of twelve inches and beveled on top. The bearing box, also of 
cast steel, is of the same dimensions as the bottom bearing, except that it 
is seven inches thick. It is beveled underneath to receive the top bearing 
and is flat on top. On it rests the cast steel breaker block, into which 
the housing screw fits. The breaker blocks are protected by brasses, 
which are placed in sockets on the tops of the blocks. 

Hydraulic Shears: Immediately beyond the forty inch mill delivery 
table, begins the No. 1 shear table, delivering to a hydraulic bloom shears. 
This table is thirty-one feet long, and consists of fourteen cast steel rollers, 
twelve inches in diameter and five feet eleven and one-quarter inches wide. 
These are driven by a Westinghouse 30 h. p. 220 volt series wound D. C. 
motor, controlled either at the bloom or the billet shears. At the end of 
this table is an emergency shear. It is a vertical hydraulic shear, using water 
at 500 pound pressure to the square inch; the plunger is forty-two inches in 
diameter with a nineteen inch stroke.. The bottom shear knife is the 
one actuated by the plunger; the knives are twenty-seven inches wide and 
four inches thick. As this is an emergency shear, it is rarely used. 

Steam Shears: No. 2 shear-table is immediately beyond the hydraulic 
shears and has thirty-six driven rollers, and one idler, all similar to those 
at No. 1 shear-table, except the last two, which are collared on one end. 
The rollers are driven by a Westinghouse 50 h. p. 220 volt series wound D. C. 
motor controlled at the steam shears. This table delivers the blooms and 
slabs to the steam shears, the center of which is ninety-two feet ten and one- 
half inches beyond the hydraulic shears. A bloom stamping machine is 
located on this table midway between the two shears; it is of the idler wheel 
type and is held in place hydraulically. The steam shears are driven by a 
MacKintosh-Hemphill 18" x 20" simple vertical steam engine, the driving 
shaft of which is meshed with the shears by a hydraulically operated clutch. 
These shears are also vertical acting, the top knife blade being driven 
down to meet the fixed lower one. The knives are twenty-seven and one- 
half inches wide and three inches thick, and the top one has a ten and three- 
fourths inch stroke. The steam shears are equipped with a gauge and 
stopper for cutting a number of pieces the same length; the stopper can be 
set to cut lengths from twelve inches to one hundred thirty-six inches, 





TWO-HIGH BLOOMING MILL 


373 


inclusive, in quarters of an inch; the piece to be cut is run through the shears 
onto the rear table, which is sixteen feet long and consists of sixteen 
hollow cast steel rollers, ten inches in diameter. It is driven through 
universal joints by a Westinghouse 19 h. p. 220 volt series wound D. C. 
motor and can be tilted at its receiving end hydraulically to move down 
with the shear knife. For pieces forty inches long or less, it is moved 
nearer the shears to prevent the piece from falling into the pit for butt ends. 
Beyond this table is the loading table for blooms and slabs; it is seventeen 
feet long and has sixteen hollow cast steel rollers eight inches in diameter. 
It is driven from a line shaft by the same type of motor as the shears rear 
table. Halfway down this table on its inner side is a steam kicker with a 
seven inch by four feet nine inch cylinder, which slides the bloom down 
a chute to the buggies on the tracks below. A hydraulic stopper is located 
at the end of this table. Crop ends or scrap can be run over the end of the 
table to charging boxes below the end of it. Six feet six inches beyond 
the end of this table begins the receiving table of a fourteen inch continuous 
mill. 

Manipulator: All reversing mills are provided with manipulators for 
turning the ingot as desired between the passes, for moving the piece from 
groove to groove and for straightening it as it enters the passes of the mill 
when such straightening is necessary. They are located under the roll 
table, and near the rolls on the entering side of the mill. They are of various 
forms. The manipulator for this mill consists of two parallel sets of five 
fingers each, and has both a vertical and horizontal movement. The frame 
is beneath the table rolls and rests on a bottom frame which is supported 
on four heads, connected to the arms of bell cranks. These cranks are 
supported on a bed plate and are connected up by stretcher rods to a 
hydraulic lifting cylinder, which has a stroke of fourteen and three-fourths 
inches. This ratio of the length of the crank arms, however, increases this 
lift to eighteen inches. On this frame are five rails to form a track 
for the wheels of the upper frame which is moved horizontally by means 
of a hydraulic cylinder. In the lowest position, the fingers are five inches 
below the top level of the roll tables; in the highest, they extend thirteen 
inches above it. 

Design of the Rolls: All reversing blooming mill rolls are designed 
with slight collars between the passes in order to control the spreading of 
the material under the heavy reduction, as otherwise the material may 
spread so far at the surface as to cause a protrusion, or fish tailing, of the 
metal at the edges, which, becoming folded over, would cause laps. To 
prevent the collars from cutting into the steel and thus forming laps all 
the passes except the finishing are given a slight belly. A fillet at the base 
of the collars serves to keep the corners of the piece well rounded. The 
ragging on the rolls to increase the bite has already been referred to. As 
to arrangement of the passes, different plans may be pursued, as may be 
seen from a study of the accompanying drawings. The first two designs 




374 


THE ROLLING OF STEEL 














































































































BLOOMS 


375 


are for blooms, billets or slabs, whereas the third design can roll large 
blooms only and billets only in connection with a roughing mill. 

In the method shown in table 53 and fig. 60 the reduction is begun with the 
ingot on edge, but when rolling soft steel, .08% to .22% carbon, the ingots are 
sometimes rolled on the flat. This reduces the number of passes to seventeen, 
the steel receiving only four passes in the first groove. In rolling blooms 
of other sizes and slabs, about the same procedure is followed out, the steel 
being given a sufficient number of passes to work it down to the required 
size. In rolling some of the special steels, such as special drop forgings, 
etc., it is often the practice to turn the steel after each pass in order to 
avoid all danger of rolling in laps and seams. Sometimes where fairly sharp 
corners are desired on the blooms they are given extra passes to hold the 
edges up. This extra rolling is especially necessary where the blooms are 
to be reheated in a continuous furnace, since if the corners are very rounded 
the blooms, instead of sliding down, are liable to roll over the skids in the 
bottom of the furnace. Furthermore, if the steel shows a tendency to 
crack, the roller may nurse it along by taking lighter drafts: 

Operation of Rolling: The sketch referred to above shows how an 
18" x 21" ingot is broken down to a 6" x 4" bloom in nineteen passes This 
sketch, combined with the following table, gives about all the information 
there is to give on this part of the work. 


Table 53. The Rolling of an 18" x 21" Ingot. 


No. OF 
Groove 

Size of 
Groove 
on Roll 

No. of Passes 
and Manipulation 

18" x 21" Ingot 
Reduced to 

1 

24" 

2 

—Bloom turned 90° 

183^" x 19" Bloom 

1 

24" 

4 

—Bloom turned 90° 

12" x 193 4" “ 

2 

12" 

4 

—Bloom turned 90° 

11 M"X 12 y 2 " « 

2 

12" 

2 

—Bloom turned 90° 

7M" X 12*6" “ 

3 

8" 

2 

—Bloom turned 90° 

V/ 2 " X 8M" * 

3 

8" 

2 

—Bloom turned 90° 

X 

OO 

5 

4" 

1 

—Bloom turned 90° 

6%" x iVs" “ 

4 

6" 

1 

—Bloom turned 90° 

hVi " X 4M" “ 

4 

6" 

1 

—Finish 

19 Passes 

4" x 6" 






















376 


THE ROLLING OF STEEL 





















































































































BLOOMS 


377 




Top and bottom rolls have same dimensions 


Fig. 63. A 38-Inch Reversing Blooming Mill Designed to Roll a Fixed Size of Bloom, 

SECTION IV. 

EXAMPLES OF THREE-HIGH BLOOMING MILLS. 

Plan of Study: Since a good idea of the relative dimensions of the 
different parts of the blooming mill may be gained from the preceding 
detailed description of the forty inch mill at Duquesne, such details, for 
the sake of brevity, may now be omitted, and the description of the forty 
inch three-high mill at Edgar Thomson be made more general with the idea 
of emphasizing the difference in construction and operation between the 
two-high and the three-high blooming mills, only. 



































































































































































378 


THE ROLLING OF STEEL 


The Engine and Connections: A tandem compound condensing 
engine, size 50" x 78" x 60", furnishes the driving power for the mill. The 
engine is housed in an engine room separate from the mill. It is provided 
with a 75-ton flywheel, twenty-five feet in diameter, and runs at a speed of 
54 r. p. m. This flywheel, supported between suitable bearings, is mounted 
upon the driving shaft, which is connected, by means of a crab and coupling 
box to the driving spindle. This spindle is nine feet eight and one-half 
inches long, including ten inches at each end for the wobblers, and twenty- 
one and three-fourths inches in diameter. It is supported at its center 
by a stationary carrier bearing, and, extending through the wall of the 
separate engine room, connects the driving shaft of the engine to the middle 
pinion of the mill. 

The Pinions and Spindles: The pinions, contained in three-high 
housings similar to the roll-housings, are six feet four inches long over all, 
and, when in place, measure forty inches from center to center of any two 
adjacent ones. The lengths of the necks are twenty-one inches and their 
diameters are twenty-two inches. These pinions are of the herring bone, 
or helical toothed type. Unlike the reversing mill, where the use of a 
vibrating spindle makes it necessary to set the pinions at some distance 
from the mill, the three-high mill will be set with the pinions as close as 
possible to the rolls; the roll spindles are, consequently, much shorter. 
The spindles for this mill are four feet ten and three-fourths inches long 
over all, and twenty-one and three-fourths inches in diameter. Each 
spindle is supported at its center by means of a bearing mounted on a bar 
that bridges the space between the inside roll housing and the opposite 
pinion housing. Specially designed coupling boxes connect the spindles 
with the pinions and the rolls. 

The Roll Housings are of the open top type. At the top the window 
of the housing is closed with a heavy cap, which is securely fastened to 
the columns of the housing by means of heavy key bolts, the slotted ends of 
which extend up through and above the ends of the cap. The screw down 
passes downward through the center of the cap and rests on the top of the 
upper bearing of the top roll, so that the pressure may be applied directly 
over its center. The rigidity of the housings is increased by the use of 
brace rods which extend from a height about the center of the top roll, 
both fore and aft, to an anchorage provided by projections on the shoes. 
The two housings are tied together by means of separators and bolts on 
front and back attached just below the caps of the housings, so that they 
are almost on a level with the upper side of the top roll, in width the 
housings measure seven feet eight inches from center to center of the shoes, 
and are approximately fourteen feet high from the lowest point in the base 
to the top of the cap. 

The Rolls are all of the same length and diameter of neck. The lengths 
of the bodies are seventy-six inches, while the dimensions of the necks and 



THREE-HIGH BLOOMING MILL 


379 





/ 


. 64. Sketch of Three-High Blooming Mill. 










































































































































































































































































380 


THE ROLLING OF STEEL 


wobblers are the same as for the same parts of the pinions. As to the diam¬ 
eters of the bodies, the three rolls are made different, the top roll being 
the smallest and the bottom roll the largest and the middle roll of an inter¬ 
mediate size. These diameters are such that the distance between the 
centers of new rolls on new bearings is forty and fifteen-sixteenths inches 
for the bottom and middle rolls and thirty-nine and eleven-sixteenths inches 
for the middle and top rolls. This arrangement, the necessity for which 
will be explained later, has the effect of throwing the rolls slightly out of 
line with the pinions which measure forty inches from centers to centers. 
This difference is distributed by centering the bottom roll five-sixteenths 
inch below the center of its pinion and the top roll five-sixteenths inch 
above the top pinion. The center of the middle roll is then five-eighths 
inch above that of the middle pinion. The rolls are designed for seven 
passes as shown on the accompanying sketch. The ingot, having been 
reduced from 23%" x 23%" to 15%" x 18%" by four passes on a forty-eight 
inch two-stand tandem bloomer, enters the first bottom pass of the forty- 
inch mill on edge and is reduced in this and the six succeeding passes to a 
9%" x 9%" bloom. Hence, all the mills of the plant using blooms from 
this mill are adjusted to take this size of bloom. It will be observed that 
the edges of the collars are well rounded off to prevent the formation of 
fins that might cause laps, and that the pitch line for the bottom passes 
lies well below the clearance line of the rolls. The bottom and middle 
rolls are made of steel, while the top roll is a sand roll. The greater strength 
of the two lower rolls is required for the greater draught taken in the bottom 
passes, which are edging passes. 

Lifting Tables: The mill is provided with two lifting tables, each of 
which is twenty-one feet seven and nine-sixteenths inches long from center 
to center of the first and last rolls. Each table has a vertical motion only, 
and is supported on four legs or vertical shafts, one at each corner, which 
are connected to lever arms mounted on shafts with other arms for counter 
weights and lifting. The torque of the counter weight just about equals 
that produced by the table. The material is then raised and lowered by 
a reversing electrical motor, which is provided with a magnetic brake for 
automatically stopping the tables at the correct levels. By means of a 
long lever arm, the two tables are connected and are raised and lowered 
in unison. The one on the approach side of the mill is provided with 
stationary vertical skid bars, or transfer fingers, between the table rolls, 
which are so arranged that the act of lowering the table edges and trans¬ 
fers the piece to the next bottom pass. The bloom from the forty-eight inch 
mill is edged to enter the forty inch mill by means of single collar rolls. 
Shears of the side cutting type, electrically operated, are provided fifty- 
six feet from the roll table for cutting the piece into blooms of the desired 
length after the required discard has been sheared off. 




THREE-HIGH BLOOMING MILL 


/ 


381 


Roll Design for Three=High Bloomers: The peculiarities, previously 
pointed out, in the. size, the arrangement, and the grooves of the rolls for 
this mill are common to three-high bloomers, and represent the effort on 
the part of the designers of the rolls to overcome certain difficulties inherent 
in this type of mill. First, in order to avoid weakening the rolls by increas¬ 
ing their length unduly, only a small number of passes, usually nine, are 
available. Second, except at rail mills, which are the only mills in exist¬ 
ence where any preliminary reduction of the ingots is made, this limited 
number of passes means that very heavy drafts must be taken in order to 
reduce the ingot to the more common bloom sizes. Third, in order to get 
in the greatest possible number of passes on a set of rolls, the passes must 
be placed one above the other, hence a groove in the middle roll must 
serve for both an upper and lower pass. Fourth, the peripheral speed at 
the base of the grooves in any two rolls forming a pass must be equal, or 
nearly so, if the piece is to roll without curling when coming out of the 
pass. However, the pass diameter of the top roll for any pass may be a 
little larger than the bottom, for then the piece will be held down but 
may be prevented from curling down by the guards on the mill. On forty 
inch mills this difference is about one-fourth of an inch and is determined 
by practice. 

An Example of Roll Design for Three=High Blooming Mill will 

perhaps be the best answer to the question as to how all these conditions 
are met. A specific problem and a method of solving it are hereby given: 

Given: Ingot 21" x 23", Bloom 9" x 10", number passes 9, Size of Mill 42". 
Required: To design rolls for the mill. 


Solution:—First: The draught on each pass is found. In finding 
the draughts it is to be borne in mind that the draughts on the bottom passes, 
being edging passes, should be heavier than on the top passes; that it is well 
to take the heaviest draughts on the first bottom passes while the steel 
is hot and the piece is short, which will prevent great strains on the engine 
as the momentum of the fly wheel will carry across a short length; that 
the top passes are best made of equal draughts; and that little work can 
be done on the finishing pass. The reduction in size of the ingot to the 
bloom calls for twelve inches on one side and thirteen inches on the other, 
or a total of twenty-five inches. Since the reductions on the bottom passes 
are to be greater than those on the top, let this total draught be appor¬ 
tioned to give ten inches on top passes and fifteen inches on bottom ones. 
The draught on each top pass will then be two and one-half inches. The 
draught on the bottom passes may be arbitrarily apportioned, but to accord 
with the cautions stated above, they are determined by trial, and to give 
the total reduction of fifteen inches they should, apparently, be apportioned 
as follows: No. 1 pass, 33^"; No. 3 pass, 3%"’, No. 5 pass, 33^"; No. 7 pass, 




382 


THE ROLLING OF STEEL 


\ 


3 y±"\ No. 9 pass, 1". The complete plan for working the ingot down to 
size would then be as follows: 

Size of the original ingot, 21" x 23". 

No. 1 Pass, bottom, draught 334"> size of bloom produced, 21" x 1934"- 

No. 2 “ top “ 2^"; “ “ “ 21" x 17". 

Piece edged. 

No. 3 Pass, bottom, draught 3%"’, size of bloom produced, 1734" x 17". 

No. 4 “ top, “ 234"; “ “ “ “ 1424" x 17". 

Piece edged. 

No. 5 Pass, bottom draught 334"> size of bloom produced, 1434" x 1334"* 
No. 6 “ top, « 234"; “ * “ “ 1424" x 11". 

Piece edged. 

No. 7 Pass, bottom, draught 334"; size of bloom produced, 1134" x 11". 

No. 8 “ top, “ 234"; “ “ “ “ 9" xll". 

Piece edged. 

No. 9 Pass, bottom, draught 1"; size of bloom produced, 9" x 10". 


Second: The most suitable pitches for the rolls are determined. 

By pitch is meant the distance from center to center of a pair of rolls with¬ 
out clearance, or the distance between any two of the pitch lines. These 
are based on the size of the mill; the average pitch for the top and bottom 
sets of passes are equal to its size, and should be such, for reasons already 
noted, that each roll will be approximately one-fourth inch less in diameter 
than the one above it. The pitch is, therefore, determined by trial as 
follows: In this case the proper figures appear to be 

4034" from center to center of top and middle roll. 

4334$" “ “ 11 “ 11 bottom and middle roll. 

(84"-f-2=42"=the size of the mill.) 

From these figures the working diameter of the passes are found as 
follows: 


2 


4334s" pitch of bottom and middle roll. 

193^" height of first pass, (See size of bloom for No. 1 pass.) 

23^" pass diameter of first pass. 

11%"— he''=11%" first pass radius of bottom roll, or first pass working 
diameter=233^". 


ll% // +3i6 ,/ =ll3 / 8" first pass radius of middle roll, or first pass working 

diameter=23% ,/ - 

+17" (size of No. 2 pass)=28^$". 

40(pitch of top and middle roll)—28 j^ 5 ,/ =12", first pass radius of 
the top roll; or first pass working diameter of top roll=2"xl2"=24". 

As this diameter is a little larger (34") than that for the middle roll, 
the pitches assigned above are assumed to be the proper ones. 






THREE-HIGH BLOOMING MILL 


383 



Fig. 65. Roll Design for 42" Three-High Mill. Scale L 













































































































































































384 


THE ROLLING OF STEEL 


Third: The size of each roll is determined. As a preliminary step 
to finding the size of the rolls, the diameters of the middle and bottom 
rolls may be assumed to be the same as their pitches, forty-three and one- 
eighth inches. The pitch size for the middle and top roll is forty and 
seven-eighths inches, and if from twice this pitch the diameter of the 
middle roll is subtracted, the pitch diameter of the top roll is the result, 
which in this case w T ould be thirty-five and five-eighths inches. If, now, 
the diameter of the working pass in the middle roll is subtracted from this 
diameter of the roll, the result is twice the depth of the groove. 

433^"—23%"=19%". 19^"-^-2=9%" depth of first groove in middle roll. 

Similarly, 3824"—24"=1424". 14^"-^2=7^", depth of groove for the top 

roll. The sum of these two quantities is seventeen inches which checks 
with the size of second pass. But more of the piece lies in the middle 
than in the top roll, so in order to get the same height of collar, eight and 
one-half inches in each roll, it is necessary to increase the radius of the 
top roll and decrease the radius of the middle by nineteen-sixteenths inches, 
making their respective diameters forty-one inches and forty and three- 
fourths inches. The diameter of the bottom roll would then be forty-five 
and one-half inches (2 x 4334"—4024"). In order to get the proper clearance 
between the rolls, which is assumed to be one inch, these diameters are 
further reduced to forty inches, the diameter of top roll; thirty-nine and 
three-fourths inches, the diameter of middle roll; and forty-four and one- 
half inches, the diameter of bottom roll. These diameters give a much 
deeper groove in the bottom roll than in the middle, which can be over 
come by cutting down the collars on the bottom roll, which has the effect 
merely of increasing the clearance. So to balance up the depths of these 
grooves a clearance of two inches is allowed between these rolls, making 
the final diameter of the bottom roll forty-two and one-half inches. The 
finding of the depth of the remaining grooves is a simple matter. Thus, 
for example, No. 4 pass is 1424" x 17". From the depth of the pass, fourteen 
and three-fourths inches, the clearance of one inch is subtracted, leaving 
thirteen and three-fourths inches. This depth is equally divided between 
the top and middle rolls, making six and seven-eighths inches in each. It 
follows that the groove in the middle roll for No. 3 pass must be the same. 
As the depth of this pass is seventeen and one-fourth inches, the groove in 
the bottom roll must be eight and three-eighths inches, (1734"—6— 
2"=824 // ). The accompanying sketch shows a set of rolls designed 
according to the explanation given above. To take care of variations due 
to wear in the rolls and permit of their being dressed, thus increasing their 
life, the entire set is made a little over-size in diameter of body, usually 
about three-fourths of an inch. They are discarded when they have been 
dressed down to the same amount undersize. 



SLABS 


385 


SECTION V. 

THE ROLLING OF SLABS. 

The Rolling of the Slab is the first step in the rolling of plates, just 
as the bloom marks the first step in rolling the many shapes. Attention 
has already been called to the rolling of slabs on the reversing blooming 
mill. For rolling narrow slabs, the blooming mill meets all the require¬ 
ments, but the width of the slabs rolled on these mills is limited to the 
maximum spread of the rolls on account of the necessity of edging the piece 
near the last passes. In America, therefore, slabs are rolled for the most 
part on the universal mill principle, in which the width of the slab is partly 
controlled by means of vertical rolls which work on the edges of the slab. 
The slabbing mills are not true universal mills, however, but double or 
duplex mills, made up of one stand of rolls, similar to the blooming mills 
but with plain instead of collared rolls, and one stand of vertical rolls near 
to and in front of the horizontal rolls. Each mill is driven independently, 
and both are reversing. By such an arrangement larger ingots may be 
rolled than would be possible on the reversing blooming mill. Since the 
piece is not edged under the horizontal rolls, ingots varying in thickness 
and slabs of great width may be handled. The following sizes as to thick¬ 
ness and widths of ingots are rolled by the thirty-two inch mill to be 
described later, 23%" x 23%"; 26" x 40", 26" x 45", 26" x 48"; 26" x 53" 
and 27" x 57". The thickness of the ingot is limited by the maximum 
height to which the top horizontal roll may be lifted, while the width is 
controlled by the spread of the vertical rolls. In preparation for the rolling, 
the ingots are treated in soaking pits in the same manner as that already 
described for the blooming mills. 

The Thirty=two Inch Mill at Homestead as an Example of a 
Slabbing Mill: This mill is an old mill and was originally designed to 
roll armor plate. It is, therefore, somewhat larger and stronger than some 
more recently constructed slabbing mills. However, the main features and 
the principles of both the construction and operation are the same on this 
mill as those of other slabbing mills. As noted above, the mill consists of 
two separately driven stands of rolls—the horizontal and vertical stands,— 
which are best described separately. 

The Horizontal Mill : The rolls on this stand are four in number, 
arranged one above the other on the plan of a four-high mill. Only the 
two intermediate rolls actually come in contact with the ingot, however, 
the topmost and bottommost rolls being used as reinforcing or stiffening 
rolls to the two intermediate ones. All these rolls are nine feet two inches 
long in the body, but the re-enforcing rolls are thirty-two inches in diameter, 
while the intermediate ones are twenty-six inches in diameter. This 
arrangement permits a more rapid reduction of the ingot and with less 




386 


THE ROLLING OF STEEL 


power than would be possible with only two rolls, which would have to be 
of large diameters to give the great strength required. The smaller roll, 
exposing little surface to the steel, sinks into the metal with less pressure 
and is turned with less power. The four rolls are held in place by a cast 
steel housing. The necks of the bottom re-enforcing roll rest on bearings 
fitted into the bottom of the housing; this roll then supports the lower 
intermediate roll, the contact being made the entire length of their bodies. 
Lateral displacement of this lower intermediate roll is prevented by 
babbitted side bearing boxes at either end. The two upper rolls are held 
in two steel frames, one at each end, each of which is fitted with a brass 
top bearing for the re-enforcing roll and a box fitted with bottom and side 
bearings for the top intermediate roll. As these frames move up and down 
with the adjustment of the top rolls, guide bars bolted to the outer edges 
of the windows are provided to hold them in place, while liners inserted 
between the frames and the sides of the windows prevent the wearing away 
of the housings. The ends of two plunger rods rest against the bottom of 
this frame while the rods extend to hydraulic cylinders which, located 
beneath the mill and acting under a pressure of 600 lbs. per sq. in., are 
used for raising the top rolls. The rolls are lowered by means of screws 
similar to those in the blooming mill, but in this case the power for the 
screw down is obtained from a 60 h. p. motor mounted on a platform a 
little above the top of the housing. The screws rest on breaker blocks 
which serve as a safety to prevent the breaking of the rolls. The maximum 
lift of the mill is nearly forty inches. For indicating the distance between 
the rolls a gauge pole and disc are provided. The disc is mounted on top 
of one of the screws with the marking pole adjacent to it. The circum¬ 
ference of the disc is divided into 100 equal parts, while the pole is divided 
into spaces of one inch each. These divisions on pole and disc are plainly 
marked and permit the opening of the mill to be read to within 1-100 of 
an inch. The Drive for the horizontal mill is connected to the intermediate 
rolls, the re-enforcing rolls being friction driven. The motive power is 
furnished by a 40" x 54" horizontal reversing engine, which is indirectly 
connected to the leading or driving spindle of the mill. 

The Vertical Mill is located about ten feet in front of the horizontal 
mill, measuring from center to center of the rolls. Like the horizontal 
mill the vertical mill has four rolls, two of which are re-enforcing; but these 
rolls are much smaller than the horizontal ones, being only eighteen inches 
in diameter and about forty-four inches in length, or a little longer than the 
lift of the horizontal mill. The rolls are supported vertically in the housings 
by means of bearing boxes at both the tops and bottoms. These boxes are 
held in place by heavy rest bars which extend across the mill at top and 
bottom and from housing to housing, between the windows of which they 
are securely fastened. For adjusting the spread of the rolls inwardly two 
screws, acting horizontally through the sides of the housings instead of 





THE SLABBING MILL 


387 


through the top as for horizontal rolls, are provided. They bear on a 
frame that extends from the top to the bottom bearings, and are operated 
by a 50 h. p. motor through a system of gears. For spreading the rolls apart 
hydraulic jacks are used. In operating the mill, all four of the rolls are 
driven. Starting with the engine, the connections are made as follows: 
The engine, a 36" x 57" horizontal reversing steam engine, is mounted upon 
a concrete foimdation a little above the level of the bottom of the housings 
and on the opposite side of the mill from that on which the engine for the 
horizontal rolls is placed. The power is indirectly transmitted through 
two gears, one above the other, to the driving shaft, which extends from 
the upper gear to the farther side of the mill. To this shaft, the two outside 
rolls are connected by means of bevelled crown and sleeve gears, while 
a second set of gears connecting the inside and outside rolls in pairs furnish 
the means by which the driving of the inside rolls is effected. The hori¬ 
zontal rolls are run at full speed, while the speed of the vertical rolls is 
controlled by the engineer to suit that of the horizontal mill. While the 
maximum spread of the vertical rolls is about sixty-five inches, the widest 
slabs rolled are only fifty-four inches wide, because this is the greatest 
width the mill shears are built to cut. The excessive length of the hori¬ 
zontal rolls (one hundred ten inches in the body, as previously given) is 
explained by the fact that this mill was formerly used for rolling 
armor plate. 

Precautions to be Observed in Rolling Slabs: The essential part of 
the rolling is the determination of the draughts to be taken on each pass 
through the mill. This determination is made by the roller from the 
dimensions of the ingot to be rolled, the slabs desired as given on the rolling 
order sheets, the temperature of the ingot as it comes to the rolls and the 
steam pressure available for the engines. The temperature controls the 
draught in that the hotter the steel the less the pull on the mill and the 
greater is the possible draught. Uniform temperature throughout the ingot 
is also necessary to insure * good rolling, as steel hotter on one side than 
on the other causes curling of the slabs, due to the fact that steel always 
curls towards the cold side, because the elongation is less on that side. 
To assist in rolling, ingots are fed to the rolls with the hot side up and 
the small end first, thus affording a better grip by the rolls and preventing 
or lessening the tendency for the slab to curl up when leaving the mill as 
they do when the cold side is turned up. Slabs are often hotter on one 
side than the other, which condition also causes curling, due to the greater 
spreading or flowing of the steel on the hot side. Indirectly, the chemical 
composition of the ingot regulates the possible draught; high carbon steel, 
for example, cannot be heated as hot as common plate steel, hence longer 
time and smaller draughts must be taken in the rolling. The total vertical 
draught, which in all cases, except 27" x 57" ingots, amounts to about one 
inch, is taken during the first few passes. From then on, the vertical rolls 




388 


THE ROLLING OF STEEL 


are kept in contact with the steel at a pressure only sufficient to prevent 
tearing of the edges which results when no pressure is applied on the sides 
of the slab. With small ingots tearing of the steel is also caused when the 
ingots are not hot enough for good rolling but still capable of being passed 
through the rolls. In the case of large ingots that are cold, there is little 
danger of injuring them, because there is not sufficient power to roll them, 
as in the case of smaller ingots. Correct lining of the rolls is necessary to 
make good slabs, since if the rolls are crossed or are higher on one end 
than on the other the slabs curl. At the thirty-two inch mill the driving 
end of the rolls is always kept slightly higher than the other end to allow 
for the more rapid wearing of the' bearings due to the extra weight on 
that side of the mill. Above the slabs will curl in passing through 
the mill. The maximum draught, i. e., reduction in sectional area, that 
can be taken by the horizontal rolls with the steel at a good rolling 
temperature is approximately thirty square inches on the entering pass and 
forty square inches on the return pass. The difference in reduction possible 
on the entering and return passes is due to the fact that, on the return pass, 
the vertical rolls aid in pulling the slab through the mill, while they cannot 
effect any power by pushing the slab when going in the opposite direction. 
For the entering pass thirty divided by the ingot width gives the approxi¬ 
mate draught, or bite, and forty divided by the ingot width, the return 
pass bite. The last pass taken is entering, and is a pass in which very little 
pressure is used in order to straighten the plate, roll down the top ends, and 
remove the convex surface due to the spring from the rolls. 


Removal of Scale: During the rolling of an ingot the scale must be 
removed from the surface to prevent the slab, and resulting plates, from 
being pitted. The process employed in removing the scale depends upon the 
kind of steel being rolled. For removing scale on low carbon steel salt and 
water, the latter being sprayed on the slab at high pressure and the former 
thrown on with scoops, are very effective. In case of high carbon steel the 
scale sticks more firmly to the slab, and burlap sacks are used, as neces¬ 
sary, in addition to salt and water. When nickel steel is rolled, coal is 
used in place of salt, and burlap is also thrown under the rolls. Brush or 
green twigs are often employed to serve the same purpose as burlap. The 
actions of all these substances are somewhat similar. In each case the 
substance is drawn under the rolls, which tend to bring it rapidly into 
close contact with the hot metal. The material thus caught by the rolls 
is gassified by the heat, and, in an effort to escape, the gases get beneath 
the scale and carry it off with them. Coal and burlap, being less volatile 
than salt or water, are carried a little farther beneath the rolls and give 
a more violent action. Nickel scale is the most difficult of all to remove, 
and if the first scale is melted off in the soaking pits and a second formed, 
it is almost impossible to clean it off. All nickel bearing slabs are cleaned 
first on one side, then turned over by cranes and cleaned on the other side. 





SLABS 


389 


Shearing Slabs at the Thirty=two Inch Mill: From the rolls the 
slabs pass by means of motor driven roll tables to a hydraulic shear. Two 
plungers are used to operate the knife, a small one on top for lifting the 
blade and a large one on the bottom for pulling the knife down against the 
steel, thus effecting the cutting. Two Wilson and Snyder pumps, an accumu¬ 
lator and steam intensifiers comprise the operating equipment. The slabs 
are cut to length by means of a scale of marks placed on a steel slab in front 
and to one side of the shears. Graduations on this marker indicate the 
distance from the shear-blade, so by running the slab out to any certain 
mark the length of slab is indicated by the graduation. The roll table 
approaching the shear-blade is also graduated in inches of distance from 
the blade. By fixing the eye on any spot or mark on the slab at any distance 
from the knife as shown by position on scale and watching this mark until 
it is moved beneath the knife, the length of slab can be obtained. The 
size (total weight) of the slab is determined by the dimensions and gauge 
of the plate into which it is to be rolled. Since the width of the ingot 
limits the width of the slab, planning the size of the slab starts with the 
selection of an ingot of the proper size. Next, the thickness of the slab 
must be determined, and then the length. It is evident that very careful 
work is necessary in making up the mill schedule, if the steel is to be rolled 
to best advantage. All this planning is done in the mill office, and the 
shearman is generally given the lengths into which the slabs are to be cut, 
though occasionally he may be ordered to cut to best advantage. The first 
cut made on the slab is to remove the piped end. After the discard is 
sheared off, a few slabs are cut, when the piece is turned around with a 
manipulator, the bottom crops taken off, and the remainder cut into slabs. 
From the rolling sheets, the shearman gets the length of slabs ordered and 
the amount of discard that is to be taken before slabs can be cut. Cuts are 
usually made up to the center of the slab before turning it around. By 
turning the slab the shearman can tell how much steel will remain after 
taking off the bottom crop and better decide as to how he shall cut the 
remainder. Slabs are cut as ordered if possible, and if a piece is left over 
that is too large, or heavy, for any slab ordered, it is marked as an “odd” 
cut. For example, a 5000 pound slab is ordered, and, after the first slabs 
have been cut, the remaining piece is 7000 pounds, or 2000 pounds over the 
weight desired. Were this 7000 pounds to be used on a slab calling for only 
5000 pounds, 2000 pounds would be scrapped in the plate mill. This system 
is too expensive, so the slab is marked as an odd cut and placed on some 
other order. The limits as to width and thickness of slab that may be 
sheared on this shear are fifty-four inches and twenty inches, respectively. 
The percentage of discard varies from about 15% on plain steel to 35% on 
some special orders; the larger portion of the discard is taken from the top 
of the ingot on account of the segregation and piping being mostly confined 
to this section. All discarded steel is placed in open hearth charging 
buggies and shipped to the open hearth, note being taken of the special 





390 


THE ROLLING OF STEEL 


alloy steel scrap, which is kept separate from the plain steel scrap. As the 
slabs are cut, they are stamped with a serial number, beginning with one 
from the first of the year. A recorder takes down the slabs made, size, 
number, cut, etc., and enters it on the product side of the rolling order 
sheet. The weight of ingot, weight of slabs made, and weight of scrap is 
noted, and the information sent to the product department. From this 
data the practice of the mill is figured. 




BILLETS AND OTHER PRODUCTS 


391 


CHAPTER VI. 

THE ROLLING OF BILLETS AND OTHER SEMI-FINISHED 

PRODUCTS. 

SECTION I. 

THE THREE-HIGH BILLET MILL. 

General Features of Rolling Billets: A large percentage (over 50%) 
of the steel produced is rolled into material of very small section. In order 
to finish their product in one heat, the mills rolling such sections must 
start with small billets. While many blooming mills of the reversing type 
are able to roll billets as small as 4" x 4" or less, which is a size much too 
large for the majority of the smaller mills, the inadvisability of employing 
these large mills for rolling billets is at once evident, and accounts for the 
existence of the billet mill. In order to reduce the cost of the billet, the 
billet mill will be placed just after the blooming mill so as to effect the 
reduction from ingot to billet on the original heat of the former. As to 
the kinds of mills used for rolling billets, almost any mill of medium size 
may be adapted to the work. Since the section is a very simple one and 
so little in the way of accuracy as to form of section or of finish is necessary, 
about the only requirements of the billet mill is that it be heavy enough 
to handle fairly large blooms and speedy enough to reduce the piece to the 
desired size before it becomes too cold. For the larger sized billets, a 
single stand of three-high rolls placed after the bloomer serves very well, 
but for small billets that are not intended for certain special purposes, like 
forgings, for example, the continuous mill is the best mill for the purpose. 

Example of Three=high Billet Mill—The Twenty=eight Inch Mill 
at Du q uesne: As an example of the former type of mill the twenty-eight inch 
mill at Duquesne will be described, because every device is employed to 
increase the out-put, and it also is an example of how the mills are compelled 
to adapt themselves to change in conditions. This mill was originally 
designed as a rougher for a rail mill, but was rebuilt in 1907. The mill is 
fed by a thirty-eight inch two-high bloomer which reduces an l& l A" x 20A" 
ingot to a 7A" x 8^" bloom. The twenty-eight inch mill at Clairton 
placed after the forty-inch bloomer is very similar to the Duquesne twenty- 
eight-inch mill. 

Engine: The mill is direct driven by a Cooper Corlise tandem 
compound horizontal condensing engine, 44" x 74" x 54", designed to 
develop 2500 h. p. at 75 r. p. m. and 25% cut-off and to rim at 80 r. p. m. 





392 


THE ROLLING OF STEEL 


at 120 to 125 pounds steam pressure. The engine is capable of developing 
4500 to 5000 h. p. The ordinary speed is about 62 r. p. m. and the normal 
load about 1200 h. p., the maximum being about 3500 i. h. p. per pass. The 
steam consumption is about 300 pounds per ton of steel rolled. The exhaust 
from the low pressure cylinder is taken to a central condensing plant 
near the engine house; this plant is of the Weiss barometric type and 
is equipped with the following apparatus: One 20" x 42" x 24" air pump 
and two Wilson-Snyder 18" x 30" x 26" x 36" 8,000,000 gallon duplex com¬ 
pound-plunger water pumps. The engine is controlled in the engine house 
by a sixteen inch throttle valve and may be shut down quickly in an 
emergency by a sixteen inch quick-closing valve just above the throttle. 

Drive: The crank shaft is connected through a flexible coupling to 
the spindle shaft. The cast steel coupling, five feet six inches in diameter 
is keyed tight to the crank shaft of the engine with a bronze half thrust 
collar over the half coupling; a .80% carbon steel wearing plate is screwed 
to the outboard bearing support of the engine and separates the collar from 
it. Eight two and three-fourths inch bolts hold a second half coupling to 
the first one. The former fits over a cast steel hub keyed to the engine 
end of a cast steel spindle shaft, twenty inches in diameter. The engine 
end of the spindle shaft is slightly curved to promote flexibility. The spindle 
shaft is seventeen feet eight and one-half inches long and twenty inches in 
diameter, and three feet seven and one-half inches from its end is the center 
line of a 20" x 48" ring oil bearing, which supports the mill end of the spindle 
shaft. The oil bearing is held in a cast iron yoke and base, mounted on a 
cast iron hot plate. The bearing is lined with babbitt and is provided with 
small oil grooves for lubricating. A tight crab, four feet in diameter, of 
cast steel is keyed to the mill end of the spindle shaft; two and one-half 
inch bolts hold a four foot cast steel loose crab to the tight crab. A 
cast steel compound coupling fits over the mill end of the loose crab and 
the adjacent wobbler of the leading spindle. The cast steel leading spindle 
is three feet ten and one-half inches long and sixteen inches in diameter. 
A plain cast steel coupling box joins the leading spindle to the middle of 
the mill, fitting over the adjacent wobblers of each. 

Pinions and Their Housings: The pinion housings for the twenty- 
eight inch mill are steel castings bolted to the mill shoes; the housing 
windows are seven feet three inches deep from the top to the sill and twenty- 
six inches wide; one forged steel liner one inch thick is used on each sill, 
and each window is faced on each side with a one inch forged steel liner. 
These are all bolted to the housings. All these liners are forged steel of .40% 
to .50% carbon. The pinions are steel castings of the helical tooth type. 
They measure thirty-six inches in length of face, and have thirteen teeth 
with a pitch diameter of twenty-nine inches. Their diameter at the shrouds 
is twenty-seven inches, and the necks taper from seventeen and three- 
eighths to seventeen inches in diameter; the wobblers are sixteen inches in 




THREE-HIGH BILLET MILL 


393 


diameter. The total length of the pinions is nine feet two inches. All six 
pinion bearings are of the same pattern, being made of cast steel with three- 
fourths inch babbitt and four narrow brass plates set 90° apart. The 
bottom bearings rest flat on the housing sill liners, no beveling being 
required; the bearings are twenty-three inches wide, twenty-eight inches 
high, and twenty-three and one-half inches through. The cap for the 
pinion housings is a solid steel casting fitting over both housings; it has 
slots at its four corners for key bolts to hold down the pinions tightly beneath 
it. Steel eye bolts are set in the caps, so that they can be lifted easily. 
The housings are held in line also by steel separator rods on each side, 
top and bottom. The bottom and top pinions are driven by the middle 
pinion and all three are connected to their respective rolls by cast steel 
coupling boxes and cast steel spindles, unsupported. 

Housings and Roll Bearings: The roll housings are cast steel, closed 
at the top with a cast steel cap; the housings are bolted to cast iron mill 
shoes. The windows of the housings are nine feet two inches deep and two 
feet nine inches wide. Three feet one and one-fourth inches above the sill 
is a ledge on which rests the bearing for the middle roll; this roll is 
held stationary, the others being adjusted to it. Bearings for this mill are 
as follows: Bottom roll: two steel carrier bearings with babbitt and 
brasses. Middle roll: same, and two rider bearings with similar babbitt 
and brasses. Top roll: two forged steel babbitted saddles for carrying 
the roll; two cast steel rider bearings with babbitt and brasses. The 
middle roll is held down on its ledge by three and three-quarter inch rods, 
which are in turn held down by two five inch set screws of one and three- 
quarter inch pitch through the caps; the rods press on the rider bearings 
of the middle roll. The screws are adjusted by means of wrenches which 
fit over nuts at the top of the screws. The carrier bearing of the bottom 
roll rests on a seat which is fastened to a seven-inch screw running up from 
below the housing through its center; this screw turns in a charcoal iron 
nut shrunk in the mill housing, and is regulated by a gear and pinion con¬ 
nection from outside the housing. The gear is moved by a vertical rod 
with a slotted wheel in the top; a hand lever is used to turn this wheel, 
and thus the bottom roll is raised or lowered. The top roll is held up by 
two counterweights through steelyard rods in each housing reaching up to 
the top roll’s carrier bearing; the roll is held down at each end by a single 
seven-inch screw of one inch pitch reaching through the cap to the breaker 
block on the rider bearing. The screw is adjusted like a bolt, with a short 
wrench usually turned by a crane. 

Rolls: In this mill the top and bottom rolls are similar and inter¬ 
changeable, while the middle roll differs in that the barrel of the roll has 
larger diameters than the bottom roll in those passes in which it acts as 
the top roll, and smaller diameters where it acts as the bottom roll when 
paired with the top roll. In passes Nos. 1, 3, 5 and 7 the diameters are 




394 


THE ROLLING OF STEEL 



Fig. 66. Three-High Billet or Roughing Mill. 


■J!LJU»JUC6j 















































































































































































































THREE-HIGH BILLET MILL 


395 


larger in the middle roll than in the top and bottom and in Nos. 2, 4 and 6 
they are smaller. The rolls are thirty and three-eighths inches in diameter, 
eleven feet four inches long over all and six feet four and one-half inches 
long in the body; the passes are shown in the accompanying sketch. 
One-sixteenth inch ragging is used. The rolls are made up in sets 
of four,—two middle rolls, one top, and one bottom roll making 
up the set. The rolls are changed every two weeks, when a new 
middle roll is inserted and the bottom and top interchanged, as 
only passes Nos. 1, 3, 5 and 7 have been used in the bottom roll and passes 
Nos. 2, 4 and 6 in the top roll; all seven passes have, of course, been used in 
the middle roll. At the end of a four weeks’ period, the entire set is returned 
to the roll shop for dressing. About five sets are kept in stock. Recently 
the diameter of the rolls have been increased, which permits more dressings 
and gives longer life. Both adamite and sand cast iron rolls are used here, 
as the reductions of the piece are small and no great strength is required. 
Adamite rolls are annealed and are very hard. The sand cast rolls are 
ordinary cast iron of the following composition, approximately: 1.87% 
total carbon, 1.22% graphitic carbon, .65% combined carbon, .37% manga¬ 
nese, .070% sulphur, .920% phosphorus, .70% silicon. The rolls weigh 
18,000 to 19,000 pounds each. The passes are 7 H", 73^", 6/4") 634"> 534”> 
534" and 4" wide. The sketch, (Fig. 66) shows the relative dimensions. 
When new, the rolls have a collar of thirty and three-eighths inches diam¬ 
eter and three-fourths inch is taken off at each dressing of the cast iron 
rolls and one-fourth inch for the adamite rolls; the rolls are scrapped when 
the collars have been turned down to a diameter of twenty-eight and one- 
fourth inches. 

Guide Cages: Two inches above the center line of the bottom roil, 
lugs are attached to front and rear of the roll housings to support guide 
cages. These cages are cast steel frames for holding up the guides used 
on all passes of this mill. They are bolted to the housings. The front 
guide cage is six feet six and three-fourths inches long, reaching almost to 
the face of the housing, and is about five feet high. It contains closed holes 
in front of all passes using the bottom roll and in front of No. 6 pass of the 
top roll; slots are provided in front of Nos. 2 and 4 passes. The rear guide 
cage is practically the same as the front but has all open slots in front of 
the top roll passes. Cast steel guides and side guards are bolted to these 
guide cages. 

Tables: The bloom from the thirty-eight inch mill comes from the 
shear tables to the engine side of the roll table for the twenty-eight inch 
mill. This table, together with the rear table, is of the lifting type and 
is raised and lowered as a unit with the rear table. The front table contains 
twelve cast steel rollers, each of which has five collars for turning the 
billets. The size of these collars, beginning at the engine side, are: 16" x 
2", 14" x 123^", 15" x 12K", 16" x 12^", and 16" x 13^". This arrange¬ 
ment allows four grooves, 93^", 83^", 7/4" an d 6" from end to end. The 




396 


THE ROLLING OF STEEL 


diameters of the rollers at these grooves are 9", 10", 11" and 12", respect¬ 
ively. The rollers are driven by a Crocker-Wheeler 75 h. p., 220 volt 
series wound D. C. Motor. There are side guards on the edges of the table 
and at the front end are side guards for putting the bloom from the thirty- 
eight inch mill into the proper pass and for protecting the other grooves. 
The table is thirty-four feet ten inches from center-line to center-line of 
the end rollers and is about six feet wide, inside. Coupled to the front of 
the table at the last groove is an extension table consisting of four dead 
rollers protected by side guards; it is fifteen feet long and fourteen inches 
wide and is used as an extension for the bar when ready for the seventh 
pass of the mill. Both front and rear tables are raised and lowered by 
means of fourteen and twenty-one inch plungers operated by a hydraulic 
cylinder; the hydraulic apparatus is located under one end of the front table 
and is comiected to each table by bell-cranks from a main shaft attached to 
the cross-heads. The front table is equipped with a stationary manipulator 
for advancing the bars from pass to pass; it consists of four sets of three 
and one set of two cast steel fingers bolted to pedestals on the foundation 
of the mill. The -fingers are set between rollers Nos. 1 and 2, 4 and 5, 7 
and 8, 9 and 10, and 11 and 12, in line with the wide collars; they are flat 
cast steel plates mounted vertically and with their tops bent at an angle 
giving a 45° slope in the direction it is desired to move the piece. The 
fingers do not reach above the level of the pass when the table is elevated 
and the bars run out on the collars of the rollers; as the table sinks, the bars 
encounter the stationary fingers and slide down into the next groove. The 
rear table, as mentioned, is operated through the same shaft as the front 
table, but owing to the fact that it must raise the bars from the lower 
roll to the middle one and advance them one pass, it has to travel through 
an arc in rising to bring its grooves in line with the next passes. This is 
done by causing the table to slide toward the next pass as it is raised by 
the use of pull-over rods attached to pedestals on the proper side of the 
bottom of the scale pit; when lowered, the table slides back into place 
again. The table consists of twelve cast steel rollers, fourteen inches in 
diameter, and six feet wide, set three feet two inches apart, making a table 
thirty-seven feet long; the rollers are driven by a motor similar to the one 
used on the front table. Rollers Nos. 2, 3, 4, 5, 6, 8, 10, and 12 have 19"x 
4" collars on their ends for turning the piece, which should tumble off 
them as it comes from the seventh pass. In addition there is a manipulator 
in the first groove; this consists of five forged steel fingers two and one- 
fourth inches wide mounted on rocker arms attached through a shaft to a 
plunger in a cylinder pivoted to a support on the floor of the scale pit. The 
upward motion of the table draws the fingers with it and, when the plunger 
stops rising in the cylinder, causes them to turn the piece and advance it 
for the second pass. This manipulator lies below the table when material 
is delivered from the bottom roll and acts only to turn bars 90° from the 
first pass to the second. The table is equipped with three heavy cast steel 




CONTINUOUS BILLET MILL 


397 


side guards between the four passes which the material uses in the bottom 
roll. These reach back nine feet from the front to the table; there are also 
light side-guards at each end of the rollers reaching the length of the table. 
These tables make the operation of the mill practically automatic, and 
make it possible to roll four pieces at the same time. 


SECTION II. 

THE CONTINUOUS BILLET MILL. 

General Features of the Continuous Mill: The continuous mill, 
often called a Morgan mill after the inventor, Chas. H. Morgan, consists 
of a series of horizontal roll stands arranged one after the other, so that 
the piece to be rolled enters the first stand and travels in a straight line 
through the mill to the last stand where it issues as a finished bar, thus 
making but one pass through each stand of rolls. In such a mill, where 
the piece is being rolled in several different stands at the same time, it 
is necessary that the surface speed of the different sets of rolls be so pro¬ 
portioned that each set will travel at a speed as much greater than the 
preceding one as the lengthening of the piece requires. With new rolls 
and perfect adjustment to produce the proper reduction, this relation of 
speed of the different stands is easily provided for by a system of driving 
gears. To care for the wearing down of the rolls, the bottom roll is made 
adjustable, and as a further precaution against little irregularities that 
can’t be overcome by adjustments, each set of rolls is purposely set to 
run at a slightly greater speed than that required to conform to the speed 
of the preceding set, so as to put the piece under tension at all times. For 
turning the piece between passes twisting guides are employed. 

Advantages and Disadvantages of Continuous Mills: High out-put 
and low labor costs are the two chief advantages of this type of mill. In 
addition, the mills roll the metal down very rapidly, thus giving less time 
for oxidation and permitting more working in one heat, and yet the speed 
of the roll is low, so that comparatively little power is required to run them. 
Besides, the scrap losses are low, due to the fact that they can roll from 
blooms of any length, which fact makes it unnecessary to cut the bloom 
after leaving the bloomer, except to discard for pipe or other flaws that 
occasionally occur. Finally, the rolls are so short as to be almost un¬ 
breakable, and, therefore, very light rolls may be used for comparatively 
heavy work with entire safety. As to the disadvantages, the great number 
of rolls not only makes the first cost of the mill very high but adds im¬ 
mensely to the cost of rolls for different sections. For the same reason, 
much time is required for roll changes. Hence, the mill is best adapted 
to roll large amoimts of one section continuously. It is obvious that com¬ 
plicated sections or those requiring great accuracy cannot be rolled on 



398 


THE ROLLING OF STEEL 


such a mill. These characteristics of the continuous mill, however, make 
it particularly well suited for rolling billets, strips, such as hoop and cotton 
ties, and skelp. They are also employed as roughing rolls for the various 
combination mills. 

Example of Continuous Billet Mill: As an example of the continuous 
billet mill the fourteen inch number one mill at Duquesne has been selected, 
because it is fed by the forty inch blooming mill, previously described. By 
this combination the ingot is rolled down to a bloom approximately 6" x 4" 
in the forty inch mill from which it is delivered on roll tables, after the 
proper discard at the shears, to -the continuous mill, where, without 
reheating, the bloom is reduced to billets ranging in size from three and 
one-quarter inches to one and three-eighth inches square. The mill con¬ 
sists of ten stands of rolls, and is set in line with the bloomer. The distance 
from the blooming mill shears to the first stand of rolls is eighty-four feet 
eight inches. 

Drive: This mill is driven by gears from a line shaft from an Allis 
Chalmers horizontal vertical compound condensing Corliss valve 
steam engine, size 44" x 78" x 60", with an indicated horse power of 3500. 
This engine is opposite the shears and is set so its driving shaft extends in 
a direction parallel to the mill line. The engine is designed to run at a 
speed of 75 r. p. m. at a steam pressure of 130 lbs. The maximum torque 
the engine is designed to give at the roll circumference is 450,000 inch 
pounds. The exhaust of this engine is taken to a central condensing plant. 
The line shaft is coupled to the crank-shaft of the engine as follows: A 
cast steel hub is forced on and held by keys to the end of the crank-shaft. 
A phosphor-bronze thrust collar is bolted in halves over this joint. The 
outer end of the hub, three feet ten inches in diameter, is bolted to a short 
steel hub having wobblers twenty inches in diameter on its other end. A 
cast iron coupling six feet ten inches long fits over this wobbler and that 
of a similar but longer hub at its outer end. This hub is two feet seven 
inches long, of cast steel, and its large end, three feet ten inches in diameter 
is bolted to a short hub, twenty-one inches wide, which is keyed onto the 
seventeen inch end of the line shaft. The line shaft of forged steel, is made 
in two pieces, nine to thirteen inches diameter, and is seventy-two feet six 
and three-fourths inches long. At ten points on the line shaft, beginning 
at the engine end of the shaft are mitre gears respectively 4' 6", 4' 0", 3' 4^6", 
3' 11M", 5' 2**", 5' 5", V 0", 5' and 7' 11" apart; these mesh with 
mitre gears keyed on cross over shafts that lead to their respective roll 
stands. These gears are supported by bearing stands along the line shaft. 
The crossover shafts drive the mill pinions, and give to each set of rolls, 
beginning after No. 1 stand, a higher speed than that of the one preceding, 
in order to take care of the increased length of the bar. The mill ends of 
the crossover shafts are carried in bearings supported on pedestals; the 
ends of the crossover shafts have cast iron half couplings keyed to them, 
and these are bolted to other half couplings which are connected to the 




CONTINUOUS BILLET MILL 


399 


leading spindles by coupling boxes twelve and one-half inches long and 
twelve inches in diameter. All spindles, pinions and coupling boxes on the 
mill are cast steel. The pods on the spindles extend along their entire 
length. The spindles, top and bottom, are all of the same dimensions: 
two feet long, nine inches neck diameter, and nine and one-half inches body 
diameter. The leading spindles are cast hollow so that they will break 
under excessive strain before any other part of the mill, and are con¬ 
nected by plain coupling boxes, each twelve and one-half inches long and 
twelve inches in diameter, to the top pinions of the roll stands. 

Pinions and Housings: The pinions are of the staggered tooth type 
with three pods. They are four feet eight inches in total length, fourteen 
and three-fourths inches wide across the face of the teeth, nine inches in 
diameter at the wobblers, nine and one-half inches in diameter at the necks, 
and fourteen and one-fourth inches in pitch diameter of the teeth, of which 
there are fourteen. The pinion housings are cast iron, in one piece, and 
are bolted to the pinion shoes, which run the length of the mill; each pair 
is bolted together at the top as caps are not necessary. The windows 
are cast to shape to receive the pinion bearing boxes, which are bolted to 
them. The pinion bearing boxes are solid cast steel boxes, round in shape 
and with lugs on the outer ends for bolting to the housings. They are 
babbitted one-half inch deep; their dimensions are thirteen inches wide in 
the windows and eleven and three-fourths inches long. The pinions are 
joined to the rolls by solid spindles and coupling boxes already described. 

Rolls and Housings: The roll housings are charcoal cast iron about 
four and one-half feet high, bolted to the cast mill shoes; the mill shoes run 
at right angles to the rolls through the length of the ten stands. The 
housings have charcoal cast iron caps, one fitting over each. The caps are 
notched at the four corners to receive the bolts to hold them fast to the 
housings, and in the center of each side is bored a five inch hole for the 
phosphor-bronze housing nuts, in which turn the housing screws; the housing 
screws are of tool steel, twenty-four inches long, with one and one-half 
threads per inch. Each housing has a window three feet seven and 
three-fourths inches deep and thirteen inches wide, with a beveled sill at 
the bottom and a ledge, twenty-one and one-quarter inches above the sill, 
for resting the carrier bearing for the top roll. Each pair of housings is 
held in line at the top by means of cast iron separators. The necessary 
holes for set-pins and stud-bolts are drilled into the housings. The liners 
used are the ordinary steel plates of varying thicknesses. 

Adjustment of the Rolls: The method of adjusting rolls in mills of 
this type is nearly always that of lining the bottom roll up or down to the 
top roll. A cast steel screw box, therefore, is placed on the sill of each 
housing and bolted to the housing; it is 16M" x 10" and is threaded with 
nine half inch grooves, babbitted to prevent excessive wear. In each of 






400 


THE ROLLING OF STEEL 


these is placed a special screw bolt, left-hand thread for the outside housing 
and right-hand thread for the inside housing. These bolts have short 
square ends on the outer ends but longer squares on the inner ends; the 
latter may be coupled together by a cast iron coupling. Above the screw 
bolts and resting on them and the screw boxes are placed cast steel wedges 
fourteen inches long and eight inches wide, with nine half inch grooves, 
babbitted. The threads are, of course, the same as for the screw boxes. 
On the wedges are rested the bottom bearings; these are steel castings. 
On the bottom they are provided with a wedge which fits against the screw 
wedge. The bearings have one inch of babbitt metal lining and two bronze 
bearing pieces. No top bearing is necessary for the bottom roll, as there 
is no upward pressure on it and it has no other piece to support, as the 
carrier bearing for the top roll rests on the ledge mentioned in the preceding 
paragraph. The breaker blocks are cast iron, the bottom ends of the set 
screws resting directly on them. These screws are squared off above the 
threads for adjustment by wrenches, and are provided with lock nuts. 

Arrangement of Roll Stands and Guides: Owing to the fact that 
the speed of travel of the bar and hence the speed of the rolls is greater 
in each successive pass, the housings are placed closer and closer together 
as the bar is reduced to avoid danger of buckling. In order from No. 1 
stand, the center lines of the rolls are at the following intervals: 10' 0", 
9' 0", 8' 0", 7' 0", 6' 6", 6' 0", 5' 6", 5' 6", 5' 6". For the purpose of obtain¬ 
ing work on all sides of the bar and as the most convenient method of rolling, 
the bar is twisted between every other pair of rolls, and for this reason 
special guides have to be used. They are of cast steel made up especially 
for these stands, so that they will give the bar just the proper twist or keep 
it headed right to enter the next pair of the rolls. These guides are 
set usually in cast steel guide boxes bolted to rest bars that are fastened 
in ledges in the housings; where necessary, saddle bars are used to hold 
down the guides and guide boxes. All guides are wedged tightly in place 
with either steel or wooden wedges. The following is the arrangement of 
the guides on this mill: No. 1 receiving guide is a combination straight 
guide and crop shear bumper; all the rest of the receiving guides are straight; 
but the delivery guides are alternated thus: No. 1, straight;No. 2, twisting; 
No. 3, twisting; No. 4, straight; No. 5, twisting; No. 6, straight; No. 7, 
twisting; No. 8, straight; No. 9, twisting; No. 10, straight. Where the 
stands are far apart or the section is light, the bar is supported from below 
by narrow plates reaching from one delivery guide to the next receiving 
guide or else by light steel side guards. 

\ 

The Rolls: The rolls for this mill are of the following dimensions: 
Total length, four feet six inches; length of barrel, sixteen inches; diameter 
of wobbler (3-pod), nine inches; diameter neck, ten inches; weight, 1500 to 
1600 pounds. 





CONTINUOUS BILLET MILL 


401 


Table 54. Data Pertaining to Rolls for a 14" Continuous Billet Mill. 


Stand 

Composition 

No. Grooves 

Body Diameter 

Before Turning 




Top 

Bottom 

1 

Steel 

1 

13^" 

13H" 

2 

a 

1 

13^" 

13Ji6" 

3 

u 

2 

>o\ 

CO 

i—H 

13**" 

4 

Adamite 

2 

i3 y 2 " 

13M" 

5 

U 

2 

UH" 

13M" 

6 

U 

2 

uh" 

13 Vs" 

7 

Chill Iron 

4 

13 %" 

13 %" 

8 

a 

4 

13 

13^6" 

9 

a 

4 

• 14M” 

14" 

10 

a 

4 

14%" 

1W 6 " 


Six inches is allowed between the centers of the grooves when only two 
grooves are cut, but only three and three-fourths inches is allowed in the 
case of four-groove rolls. Following is a table of the speed of the rolls of 
each successive stand and the observed delivery speed of the bar coming 
out of it with the engine at normal speed of 75 r. p. m. 


Table 55. Speed Ratios on Fourteen Inch Continuous Billet Mill. 

Stand Speed of Rolls— Delivery Speed of Bar 

Revolutions Per Minute Feet Per Minute 


1 17 46.7 

2 21.4 54.5 

3 24.55 67.1 

4 30.9 99.2 

5 36.6 126.3 

6 44.6 156. 

7 57.6 188. 

8 68.7 242. 

9 89.1 326. 

10 117.9 417. 


Cropping Shears: Between the receiving table to the mill and the 
first stand of rolls are hydraulic shears, pressure 450 lbs. per square inch; 
through these shears all blooms for the fourteen inch No. 1 mill pass. They 
are capable of cutting blooms up to 7"xll" in size, but their usual work is 
on 6" x 4" blooms. They are used to cut crops from the front end of the 
bloom so it will enter No. 1 stand easily. When necessary they may be 
used for shearing off pipes and bad pieces that have escaped discard at the 




402 


THE ROLLING OF STEEL 



Fig. 67. Rolls and Passes for 




















































































































































































































































CONTINUOUS BILLET MILL 


403 








the Continuous Billet Mill. 


















































































































































































































































404 


THE ROLLING OF STEEL 


blooming mill shears, and for severing the bloom in case of a cobble. They 
are capable of a ten inch swing from the base, and at the end of their stroke 
they strike the combined guide and bumper previously mentioned as the 
No. 1 guide. They are thrown back into position automatically, when the 
bloom is cut, by a heavy coil spring. The stroke of the knife blade is ten 
inches. The shears are vertical acting with the top blade actuated by the 
cylinder. No. 10 stand delivers the finished billet directly onto the receiv¬ 
ing table for the steam flying shears; this table and its delivery table are 
driven through bevel gears on a single line shaft; the line shaft is driven 
by a jack shaft geared to a primary jack shaft which is in turn geared to 
the crossover shaft for No. 10 stand. As various numbers of stands are 
used for the various sizes of billets, the corresponding sizes of bars have 
a different delivery speed and the shears receiving table must, therefore, 
be driven proportionately, so that the billet maybe cut by the flying shears 
without buckling and may be carried away, when cut, fast enough to keep 
clear of the next billet. Accordingly, various sizes of gear wheels are 
provided for the jack shaft to the table. The surface speed of the roll 
table may be set at various rates to suit the delivery speed of the billet 
by changing the gears on the jack shaft. 

Flying Shears: The flying shears roll-table consists of eight cast steel 
rollers,—two, sixteen inches in diameter, on the receiving side of the shears 
and six, ten inches in diameter, on the delivery side. The rollers are notched 
with a V-shaped groove so as to hold the bar, as it comes to the shears, 
with one of its diagonals in the vertical, as it is in this position when it 
leaves the last pass of the rolls and must be sheared in the same position. 
The flying shears are placed with the center line of their knives twenty feet 
beyond the center line of No. 10 stand. The shears are actuated by a 
30" x 20" steam cylinder. The action of the shears is speeded up or slowed 
down according to the delivery speed of the billet. Cutting under fifteen 
foot lengths is not attempted for fear of not getting the shears back to 
position in time to prevent buckling of the next billet. The knives on the 
shears have a life of from three to sixty hours; and they have to be changed 
for every size of billet. They have a half inch clearance above the square 
being cut. The horizontal stroke of the shears is ten inches. 

Hot Beds: The flying shears deliver upon a table 125 feet long, from 
which steam operated rollers and pushers convey the bars to four hot beds 
extending at right angles to the tables. All of these are controlled from 
a pulpit in the yard. The rollers at the foot of No. 1 bed are skewed so as 
to bring the billets against the first pusher and make them lie parallel 
with it; all the other rollers are, as usual, set at right angles to the pieces. 
At four points on the table are hydraulically operated stoppers for stopping 
the bars at the hot bed desired or allowing them to pass to the horizontal 
scrap bed beyond the last hot bed. The hot beds are sloped up at a slight 
angle and are each thirty-one feet wide by fifty-three feet six inches 





CONTINUOUS BILLET MILL 


405 



Fig. 68. 14" Continuous Mill—4" x 6" Blooms to 2" Billets 

Drawings from Actual Sections. 


















































406 


THE ROLLING OF STEEL 


long. They are built of rails, and the material is moved on each by a steam 
pusher connected to a cable, driven through gears by two 8" x 10" vertical 
twin simple 50 h. p. steam engines. Cold pushers are also cable connected 
by gears and driven by similar engines, but of the horizontal type. They 
convey the billets desired to the end of the bed and slide them over rail 
ends from the beds into railroad cars just below the hot bed level. Alligator 
scrap shears are provided at the end of the scrap bed, which is hand operated. 
The accompanying prints are intended to show the forms of the 
rolls, their kinds, shape of the various passes, and the different stages in 
the reduction of the bloom to the billet. 

SECTION III. 

ROLLING OF SHEET BARS AND SKELP 

Difficulties and Methods of Rolling Semi=Finished Flats: This 

material may or may not be rolled from the original heat of the ingot. At 
Duquesne, sheet bar, as well as billets and splice bars, is rolled on the 
twenty-one inch mill from the original heat of the ingot, which, being first 
reduced to a 83^" x 734" bloom on the thirty-eight inch mill, is passed to 
the twenty-eight inch billet mill and on to the twenty-one inch mill without 
reheating. At Edgar Thomson, for example, the 934" x 934" bloom from 
the three-high blooming mill is reheated, when the rolling is completed on 
the No. 4 mill, which consists of a single train of three stands of three-high 
rolls, or on one of the rail mills, usually the number one. However, the 
method employed in reducing the material is the same, except as to details 
of handling, which, of course, must be changed to suit the different mills. 
Because’the twenty-one inch mill at Duquesne represents a distinct type 
of mill, this mill is selected as an example of a mill rolling sheet bar. The 
problem to be overcome in rolling these flats lies in the difficulty of con¬ 
trolling the width. In rolling blooms, billets and small slabs, the piece 
is held to dimensions, not only by the shape of the grooves, but also by 
edging the piece in certain of the passes. But in rolling sheet bar, the 
thinness of the piece will not permit edging, after it leaves the roughers. 

The Tongue and Groove Pass: For the purpose of controlling the 
width and at the same time effecting a heavy reduction in the sectional 
area, a form of closed box pass, called the tongue and groove pass, is used. 
In this form of pass a groove, corresponding in width to the width of the 
piece desired, is cut in one of the rolls which encloses one side and the 
edges of the piece in rolling, while a tongue, cut on the opposite roll, fits 
into the groove, thus closing the pass on the fourth side. The designing 
of this pass presents some very interesting features. In order to insure a 
proper delivery of the pieces from the rolls and provide for fitting the tongue 
into the groove, the sides of the latter are cut at a slight angle to the bottom. 
Owing to the heavy drafts taken, the metal is squeezed up into the clearance 
between the tongue and the edges of the groove, thus forming a fin on each 






SHEET BAR 


407 


» 



No. 1 Stand—4' x4" Billet, Common Splice and Sheet Bar 





y 



d 

_ J 

f 1 

Dummy Pass 

M.ll 


v rrn 








i -1 






No 2 Stand for Sheet Bar 



No 3 Stand for Rolling Sheet Bar 


7 r 


•7{T- 


No. 4 Stand for Rolling Sheet Bar 

1 

/-for No 5 Stand 

omy 

«ni® 





Nos. 5 and 6 Stands for Rolling Sheet Bar 


Fig. 69. Roll Stands for Rolling eight inch Sheet Bar, 

































































































































































408 


THE ROLLING OF STEEL 


side of the piece, unless precautions are taken to prevent it. These fins 
are prevented from forming by cutting the groove with fillets at the edges, 
and arranging them so that the bevelled edges of the piece formed by the 
fillets enter the succeeding pass opposite the openings formed by the clear¬ 
ance between the rolls. In this way no fin is formed, because the spreading 
of the material merely fills out the bevel of the fillet, leaving no excess 
metal to be squeezed up between the rolls. To enter the first tongue and 
groove roll the edges of the billet are well rounded off, which prevents 
more than a y/ery slight fin forming in this pass. Since the piece is to be 
finished in plain rolls, no fillet is placed in the last tongue and groove pass. 
The accompanying prints show the forms of these passes, and the different 
steps in the reduction from the billet to sheet bar. 




-tr— -i 

p«» 8 


Fig. 70. Rolling Tongue and Groove for 8 inch Sheet Bar. 


Sheet Bar is all approximately eight inches wide and varies in thickness 
to give weights, per linear foot, from seven toforty-three pounds. The gauge 
in inches is found by multiplying the weight per foot by .0372 in which factor 
the weight of a cubic inch of steel is taken to be .28 pounds. After the mill is 
once set for rolling sheet bar, the different weights of bar are obtained by 
varying the distance between the rolls. As there is considerable difference 
in temperature in different billets when rolled, as at this mill, from the 
original heat of the ingot, it is difficult to hold the thickness constant at 
the finishing stand, and, in order to keep the thickness uniform, a man is 
stationed at this stand of rolls to adjust the screws up or down to suit the 
temperature of the bar. As it is necessary to produce a very smooth surface 
on sheet bar, on account of its being subsequently rolled into thin sheets, 
chilled rolls are used in the finishing stands. For the same reason, water 
and steam jets must be directed against both surfaces of the bar in order 
to remove the scale. These jets are used both at the rolls and at the saws. 

Example of a Mill Rolling Sheet Bar—The Twenty=one Inch Mill 
at Duquesne: As previously stated, this mill represents a distinct type. 
The design aims to secure the advantages of the continuous mill and elimi¬ 
nate the disadvantages. So, while it is practically continuous in action the 
different stands of rolls are placed so far apart that the piece clears one 
stand before it enters the next. As a tandem arrangement alone would 


















































SHEET BAR 


409 


spread the mill out over a too great length, the various stands of rolls are 
usually arranged in trains that are in tandem. Such a layout requires long 
roll tables for carrying the piece forward and suitable apparatuses for 
transferring the piece transversely, such as lifting cradles, skids, diagonal 
roll tables, and switch, or divided, tables. In this respect the twenty-one 
inch mill at Duquesne is a good example. 

The Layout for This Mill, as for all mills of this type, is somewhat 
complicated. The mill consists of six stands of rolls arranged in two trains, 
separately driven apd of three stands each. The two trains are separated 
by a distance of 119 feet. In each train the first and second stands next 
to the engine are three-high, while the third, on the end of the train, is 
two-high. For convenience the different stands are numbered in the order 
in which the material passes through them. Observing this order, then, 
stands Nos. 1, 4 and 5 compose the first train, while stands Nos. 2, 3 and 6 
make up the second train. The first stand is located 105 feet beyond the 
twenty-eight inch mill and is provided with a receiving table fifty-three 
feet six inches long, equipped with switches for guiding the material from 
the twenty-eight inch mill into the different passes in the first stand of 
the twenty-one inch mill. These passes are three in number, all of different 
sizes, one of which is employed as a finishing pass for billets and the other 
two as working passes on material to be finished on the twenty-one inch 
mill. 

Arrangement of the Roll Tables: The delivery table for No. 1 stand 
is provided with a center guard for diverting material to the billet table 
that leads to the 4" x4" billet shears, located beyond No. 2stand. Further 
along, by means of a switching device another division of the material 
may be made, thus sending billets either through a dummy pass in No. 2 
stand to the fourteen inch No. 2 continuous mill, located about 100 feet 
beyond, or to a working pass, when the material is to be finished at the 
twenty-one inch mill. Since material must be cut into suitable lengths for 
rolling on the twenty-one inch mill, a hydraulic shear is located 77 feet 
from No. 1 stand and arranged to cut on the twenty-one inch mill-half of 
the table only. The receiving table for the No. 2 stand begins at these 
shears. It is provided with a stop which may be set for lengths from 
twelve and one-half to thirty-eight feet. A manipulator for turning the 
piece is also provided in this table. The delivery table for No. 2 stand is 
65 feet long and has ten rollers fifteen inches in diameter and twenty inches 
long; these rollers are separated by a side-guard from the rollers leading 
to the fourteen inch mill No. 2. In connection with this table is a transfer 
skid table for moving the piece to the receiving table for No. 3 stand. It 
consists essentially of a frame of rails bolted together and hinged to the 
table, onto which they are to deliver the steel. The frame, when in its 
lowest position, lies below the roller tables, so that when the transfer is 
raised, it picks up the steel, which slides down the rail skids onto the table. 



410 


THE ROLLING OF STEEL 


The skids are greased so that the steel will slide more easily. The frame 
is raised and lowered by means of links keyed to a line shaft which is in 
turn operated by a hydraulic cylinder. The transfer raises the bars twenty 
inches from the top of the delivery table No. 2 to the top of the rollers 
of the receiving table of No. 3 stand, the distance between the two tables 
being eight feet three inches. As No. 3 stand is often used as a three-high 
stand this table is of the tilting type, and operated by an hydraulic cylinder 
placed near the stand. The delivery table of No. 3 stand is 109 feet long 
and serves also as a receiving table for No. 4 stand. It is stationary and, in 
order to receive the material when No. 3 stand is operated two-high as 
well as three-high, it is inclined, extending from the top of the bottom 
roll of No. 3 stand to the top of the middle roll in No. 4 stand. Collars 
on its rolls serve to turn the piece between the stands, and its side guards 
are adjustable so that they may be used to guide the piece into different 
passes on No. 4 stand. The delivery table for No. 4 stand is 79 feet long, 
and has guards on the side next to the engine only, in order that the piece 
may be transferred by means of a skid table to the receiving table for 
No. 5 stand. This transfer table is similar to that between No. 2 and No. 3 
stands except that the piece here slides to a lower level, where it is stopped 
by the guards on the receiving table for No. 5 stand. Connecting No. 5 
and No. 6 stands is a stationary table provided with adjustable side guards 
and vertical rollers for edging the piece as required. 

Hot Saws and Shears: The delivery table of the last, or No. 6, stand 
is about 104 feet long, and at its farther end are located two electrically 
driven hot saws set thirty feet six inches apart. These saws, made of .80% 
carbon steel, are forty-two inches in diameter and one-fourth inch thick. 
This table feeds into a shear table, one hundred three feet nine inches long, 
along which are situated seven electrically operated shears. These shears 
are adjusted to cut at any lengths up to ninety-seven feet six inches, which 
is the maximum distance between the first and last shears. They may be 
made to cut in unison or separately, as desired. From the shear table the 
piece may take a straight course to the sheet bar shears and bundling cradle, 
or be diverted to the hot beds which are used for ( billets and splice bars. 
Returning now to the billets from No. 1 stand, it was mentioned that 4" x 4" 
billets could be diverted to a shear. This shear, of the duplex type, is 
located several feet beyond No. 2 stand and is provided with a bisected 
table of which each part leads to one of the two blades of the shears. A 
gauge and automatic stopper, mounted on a gauge beam about two feet 
above the delivery tables for the shears, can be set at one-quarter inch 
intervals for any lengths from twenty-three and one-half inches to twenty 
feet. From these shears, an elevated inclined roller conveyor carries the 
short billets to eight bins, each of which has a capacity of 30 tons and is 
located so as to empty directly into railroad cars by gravity. 

Drive: Each train is direct driven by a William Tod Co. 34" x 58" 
x 60" tandem compound horizontal condensing engine of 3500 h. p. The 



SHEET BAR MILL 


411 


usual speed of these engines is 67 r. p. m. but they can be run as high as 
82 r. p. m. Both trains are direct driven through a pinion shaft from the 
crank-shaft of the engine. The connections between engine and mill and 
between the stands of rolls are made in a manner exactly similar for both 
trains, so that one description will suffice for both. To the end of the 
engine crank shaft is keyed a half coupling of cast steel, and over it is bolted 
a thrust collar. A second half coupling is bolted to the one next the engine. 
A compound coupling box—two feet two and one-half inches in diameter on 
the engine end and nineteen and one-half inches on the mill end and nineteen 
and one-half inches long for No. 1 train of rolls, and a similar box but two 
feet two and one-half inches in diameter on the engine end and twenty-three 
and one-half inches in diameter on the mill end and nineteen and one-half 
inches long for No. 2 train of rolls—fits over the wobbler of the second half¬ 
coupling and the mill end wobbler of the leading spindle. The leading 
spindle for No. 1 train is three feet four and three-fourths inches long, and 
twelve inches in diameter, and has three pods on the engine and four on the 
mill end. For No. 2 train the leading spindle is four feet one and one-half 
inches long, sixteen inches in diameter on the engine end, where it has 
three pods, and twelve inches in diameter on the mill end, which has four 
pods; this spindle has twelve and one-half inches near the center turned 
smooth to a fifteen inch diameter for a rider bearing. A coupling box 
of cast steel, fifteen inches long and seventeen and one-half inches in diameter, 
connects the leading spindle to the center pinion of the three in the pinion 
housings. 

Pinions and Housings: These pinions are plain steel castings, six 
feet three inches long, with a pitch diameter of twenty-one inches, a neck 
diameter of thirteen inches, a wobbler diameter of twelve inches, and a 
width of twenty-four inches across the face of the teeth. There are eleven 
teeth, of six inches pitch, cut in the helical manner. There are three pinions, 
set one above the other in their proper bearings in cast steel pinion housings. 
These housings stand about five feet eight inches above the mill floor and 
are bolted to the mill shoes; their windows are twenty-two and one-half 
inches wide and five feet eight inches deep, beveled at the bottom, and 
are provided with forged steel side liners, five feet four and seven-sixteenths 
inches long and two and three-fourths inches thick, and cast steel bottom 
liners, 35" x 12" x 2". The housings are drilled for the necessary holes for 
set pins, stud bolts, cap bolts, etc. One steel cast pinion housing cap covers 
the housings; at its four corners are drilled four inch holes for the cap bolts 
which are three feet five inches long, and are held in by a nut at the bottom 
and a key at the top. In the middle are fastened two hooked lifting bolts, 
for enabling the crane to get hold when the caps are to be removed. The 
bearings are all of the solid type, of cast steel, and babbitted. Coupling 
boxes, similar to the one connecting the leading spindle to the middle pinion, 
connect the three pinions to their respective spindles. The spindles are 
steel castings with wobblers of four pods each, extending from end to end, 



412 


THE ROLLING OF STEEL 


they are three feet six inches long and twelve inches in diameter. They 
are supported on the mill end by another set of similar coupling boxes 
which connect them to the rolls. 

Rolls and Roll Housings: The rolls on this mill are twenty-six inches 
long on the body for all stands except No. 3 which is thirty-six inches, 
because, being a three-high stand, it contains a greater number of passes 
than the two-high stands. The collars are usually twenty-two and one- 
half inches in diameter; the body diameters range from fifteen to twenty- 
seven inches; the diameter of the necks is thirteen inches, and of the wobblers 
twelve inches. The total length is six feet ten inches for the rolls on No. 3 
stand and six feet for the rest. The rolls range in weight from 3800 pounds 
to 7000 pounds. The rolls are cut down each time they are dressed one- 
eighth to three-eighths of an inch until a collar diameter of nineteen inches 
is reached, when they are scrapped. The rolls are of the following materials 
for the various products rolled: 

No. 1 Stand—Usually sand roll; rarely steel. 

No. 2 Stand—Sand Roll for billets and common splice bars; steel in 
majority of cases for Duquesne and continuous rail 
joint; always steel for sheet bar. 

No. 3 Stand—Sand Roll for billets and common splice bar; sometimes 
the top roll for common splice bar is steel. Steel always 
for sheet bar and nearly always for Duquesne and con¬ 
tinuous rail joint; otherwise cast iron. 

No. 4 Stand—Sand Rolls always for everything. 

Nos. 5 and 6 Stands—Always sand rolls except for sheet bar; sheet 
bar requires chilled iron rolls. 

About three sets of billet rolls, about three sets of cast iron rolls for 
sheet bar and five sets of chilled rolls, two sets of common splice bar rolls for 
No. 6 stand and one set of other rolls are carried on hand. For rail joints rolls 
are turned up as needed, and all splice bar rolls are ordered new when speci¬ 
fications for a new section come in. The roll housings for the twenty-one 
inch mill are similar for stands Nos. 1, 2, 3, and 4, which can be used as 
three-high, and for Nos. 5 and 6 which are only two-high. In No. 1 train, 
the rolls in No. 1 stand are connected by spindle and coupling boxes to those 
in No. 4 stand and the bottom two of No. 4 are connected to No. 5 rolls. 
No. 2 train is similarly connected; the top roll of Nos. 1 and 2 stands is a 
dummy acting as a spindle and the bottom rolls in Nos. 3 and 4 stands 
act the same way. The spindles, except those between No. 3 and No. 4 
stands, are two feet nine inches long and twelve inches in diameter; the 
latter are three feet six inches long and twelve inches in diameter. The 
coupling boxes are all fifteen inches long and seventeen and one-half inches 
in diameter. The roll housings are cast iron, held in line, top and bottom, 
by cast iron separators. For Nos. 1, 2, 3, and 4 stands the housings stand 



DEFECTS IN BLOOMS AND BILLETS 


413 


five feet eight and one-half inches above the mill shoes and have twenty- 
two and one-half inch windows; those for Nos. 5 and 6 stands rise three 
feet eleven and three-fourths inches above the shoes and have twenty-two 
and one-half inch windows. From each housing there are two cast iron 
caps, held down by square key bolts, fitting through five inch square holes 
in the caps. In the center of each cap is cast a hole for receiving a phosphor 
bronze housing-nut, which is pressed into the cap and threaded for receiving 
the housing screw. This screw, which is made of open hearth steel of 
.36% to .40% carbon, is five and three-eighths inches in diameter at the base 
and is threaded at a one inch pitch. On all stands but No. 6, a cast steel 
rosette is fastened on top of the housing screws to provide means for turning 
them. They thus hold the top rolls tightly down. On No. 6 stand a cast 
steel disc is used instead of a rosette, and a long lever is attached 
to it, which in turn is held in place by means of bolts through slots in the 
outer edge of the disc. The bottom bearings for Nos. 1, 2, and 3 stands, 
as well as all the riders and the carrier bearings are of cast steel. Brass 
bearing pieces are used in some, but not in all, of the housings. The pre¬ 
ceding prints show how the mill may be used for rolling billets as well as 
sheet bar. The rolling of rail joints, to be described later, is gradually 
being discontinued on this mill, the intention being to transfer this business 
to Edgar Thomson Works. 


SECTION IV. 

SOME GENERAL PRECAUTIONS TO BE OBSERVED IN ROLLING 

SEMI-FINISHED PRODUCTS. 

Reasons for Studying Defects: A great many of the precautions 
necessary to observe in rolling the semi-finished products have been 
mentioned at various times in preceding pages. However, as failure to 
observe the proper precautions in rolling gives rise to defects in the material 
which may show up in the finished article and as the reader may be par¬ 
ticularly interested in this phase of the business, it is thought that a list 
of rolling defects and their causes may be found useful and interesting. 
By giving the cause for each, it will be shown that many defects are unavoid¬ 
able, and that even the most rigid inspection will not suffice to eliminate 
some defects which are a common annoyance to the manufacturer and 
consumer alike. 

Rough Surface Due to Scale: One of the defects common to semi¬ 
finished material and one that often shows up in the finished article is a 
very rough or pitted surface. That this roughness most often is due to 
the adherence of scale on the surface of the ingot during the rolling there 
can be little doubt, because a careful examination of such defects will 
generally reveal its presence in these pits. At first thought this defect is 
likely to be attributed to a rolling of the scale into the surface, and the 
remedy at once suggested is to clean the ingot of scale during rolling. But 



414 


THE ROLLING OF STEEL 


failure to remove the scale from the ingot will not always account for this 
roughness. In such cases the blame for the defect is to be laid to the 
presence of blow holes near the surface, which in the heating of the ingot 
in the soaking pit become filled with molten oxides. The presence of the 
oxide may be attributed to two causes, namely, to the oxidation of the 
surface of the blow holes or to its introduction through small openings 
which lead from the blow holes to the surface of the ingot. Thus, if the 
ingot is subject to a temperature sufficiently high to fuse the oxides, the 
oxide in the hole will melt, or the liquid oxide on the surface will flow through 
these openings to the blow holes beneath and partially or completely fill 
these small cavities. This oxide cannot be removed, and when the ingot 
is rolled, it becomes so firmly embedded in the surface that even subsequent 
pickling will not remove it. The only correction remaining for such defects, 
then, is the very expensive one of chipping or grinding. Low carbon 
chrome-nickel steel is very susceptible to this fault, and it is very difficult to 
clean the scale from its surface. While this peculiarity of nickel steel may be 
attributed to the same cause as that just cited for plain steels, there is 
much evidence to show that scale pitting in this case is partly due to an 
entirely different cause, namely, the reduction of the oxide of nickel by 
metallic iron at the rolling temperature of this steel. Thus, as fast as this 
alloying element is oxidized on the surface, its oxide is reduced by the free 
iron beneath, the result being the formation of iron oxide under the surface 
of the metal. This condition gives rise to an outer layer composed of 
metallic alloy mingled with oxide, in which the oxide acts as a binder 
between metal and surface scale. It can readily be seen that this layer 
may vary in thickness, and the merging from all metal to all oxide is gradual, 
resulting in what may be termed an interpenetration of metal and oxides, 
which causes the scale to adhere most firmly to the surface. 

Cobbling: The most frequent failure in rolling is cobbling. It occurs 
at the blooming mill as a turn down or twisting of the piece in the rolls, at 
the rougher in the same way or by catching and buckling on the roll table, 
and at the other mills as a roll table or mill accident. The piece may 
catch on a table and buckle up and be prevented from coming through the 
rolls; it may catch against a guide and buckle; or it may buckle against 
the rolls, if delivered to them too fast. In such cases, practically all of the 
piece has to be scrapped; the uninjured sections of partially cobbled blooms 
can usually be finished and be made use of. 

Laps: An over filling of a pass causes the steel to spread between the 
collars of the rolls and causes a lap; this is usually rolled down into the 
surface, partially or altogether, if the steel is turned for the next pass, 
and the place between the lap and the rest of the piece is left as a surface 
crack, or seam. A lap may result from a 'crack in the rolls into which the 
steel flows. 

Collar Marks: Owing to overdraft or possibly defective heating, or, 
in the blooming mill, to too infrequent turning of the piece, the steel will 
overfill the groove, causing collar marks. Lack of alignment or proper 




DEFECTS IN BLOOMS AND BILLETS 


415 


adjustment of the rolls or any other incident that gives an unequal draught 
will cause the collars to bite into the bloom and injure it. Collaring leaves 
deep cuts that can seldom be rolled out, hence the injured portion of the 
bloom is discarded at the shears. 

Guide Marks: Guides, if they are too deep, out of line, or required 
to do too heavy duty will score the surface of the steel, usually, in fine 
lines, or else may tear its edges. 

Ragging Marks: Ragging leaves protrusions on the surface of the 
steel, and sometimes these are lapped over, showing in the finished steel 
in irregular seams and cracks. On mills rolling steel that is to be rolled to 
small section or a fine finish, only light ragging is used. 

Off Size: If a bloom, slab, or billet is off size, it makes the weight 
of the predetermined cut different from the actual cut and will prevent an 
order from being accurately filled, or may even cause a deficit of steel to 
apply on the order. On mills of the class in question it is difficult to work 
to absolutely correct sizes, hence, a tolerance for weight as well as for 
size should be given. 

Unequal Draughts: These defects are due to the rolls being out of 
parallel with each other, causing one side to be rolled light and the other 
heavy. This condition may result also in a turning down of a lap in the 
next pass in the case of a bloom, or a cobble in the case of a billet. 

Seams: Seams may be caused by blow holes, by laps, or by tearing 
of the steel due to causes which will be explained in a succeeding 
paragraph. Slivers or scale, first rolled into the surface, and then torn 
out, may leave cracks that will roll down to form seams. Seams may also 
be caused by too much belly in the roll, or by not turning the piece often 
enough during the rolling of the bloom, as illustrated in Fig. 71. Seams 
are especially injurious in steels for forgings and for heat treatment. They 
seldom fail to cause the steel to crack in quenching, particularly if the steel 
is quenched in water. 

Slivers: Slivers are due to defective teeming of the molten steel and 
to a tearing of the corners of the steel in blooming, roughing, or finishing. 
Tearing is attributed to many things, such as over oxidation in the open 
hearth, burning, twisting in the rolls, and improperly adjusted guides. Soft 
steels and high sulphur screw stock are especially subject to these defects. 

Scabs: Scabs are found on steel if it is burned or if scale is rolled into it. 

Shearing Defects: Failure to discard properly at the shears may 
result in rejection of product. Aside from this neglect, other defects may 
be produced by the shearing. Thus, a dull shear knife or one with too 
great clearance will not make a clean cut and will leave a lip on the side 
of the steel where its stroke ends. An unavoidable effect of shearing is 
to produce what may be termed a mechanical or manufactured pipe. In 
the shearing of billets and slabs, especially in the case of 4' x 4 billets and 
larger, it frequently occurs that the sheared end shows a pulled-out con- 






416 


THE ROLLING OF STEEL 



Fig. 71 Good and Bad Practice in Rolling Blooms. 

Top bloom shows effect of not turning the bloom often enough. 











DEFECTS IN BLOOMS AND BILLETS 


417 


dition. There are a number of things responsible for this condition on the 
sheared ends. Thus, highly segregated steel will not shear uniformly and 
often results in a pulled-out condition, and the same thing is almost sure to 
happen in case the billet or bloom has a spongy center. The temperature 
at which the billets are sheared plays a very important part, also. These 
pulled-out cavities on the sheared end may have a depth of more than 
one inch. It is readily seen what happens when such billets are re¬ 
heated and rolled into small sizes. The pull-out is closed up and elongated 
with the rolling, and when rolled into a small rod or any other smaller 
shape the effect of this pull-out condition may extend far back into the 
finished material. Very often this manufactured pipe is mistaken for a 
genuine metallurgical pipe, since in most cases it is centrally located. The 
injurious effect of a manufactured pipe on the physical properties of steel 
is similar to that of a metallurgical pipe. 

Splits or Cracks in Billets and Blooms: In breaking down ingots it 
often happens that the metal does not yield properly to the draught, and 
the surface structure is cracked or torn at a number of places, and some¬ 
times to a depth of two or three inches. As the rolling is continued, these torn 
surfaces are gradually closed, but not perfectly welded, and become much 
elongated, so that it is not easy to detect them in the finished article, not 
only because they are completely closed but because of the new scale, which, 
forming after the rolling is finished, totally covers up all signs of their 
presence. This feature makes their occurrence all the more serious, because, 
though their dangerous character is recognized by the manufacturer, and 
every attempt is made to eliminate them, the inability to detect them 
often leads to their passing the inspection. These cracks are attributed 
to many causes. In the first place, certain grades of steel, more particu¬ 
larly those in which the carbon content lies between .18% and .22%, are 
more susceptible to this defect than others. The sulphur and manganese 
content also appears to affect the tendency of ingots to crack. Hence, 
many steel men are inclined to lay most of the blame to chemical compo¬ 
sition, while others hold that the fault lies in improper treatment in manu¬ 
facture. It is a fact that steel not properly made may be red short, and 
that the steel can be injured through too heavy draught and too much reduc¬ 
tion without turning, or poorly designed passes in rolling cannot be denied. 
It also appears that the heating of the ingot in the pits may exert an impor¬ 
tant influence upon the rolling properties of the steel. 

Inspection: Blooms, billets, and slabs are inspected on the mill 
yard, and when defects are not very deep, they are chipped out with chipping 
hammers, if so ordered, before the steel is shipped. All inspection is 
directed to the elimination of the defects listed above, and rejection is 
according to the strictness of the order in respect to this requirement. 
Billets and sheet bars are hot bed inspected, and in addition to inspection 
for surface defects sheet bar is also tested for exactness of weight. 



418 


ROLLING FINISHED PRODUCTS 


r 


i 


CHAPTER VII. 

THE ROLLING OF THE HEAVIER FINISHED PRODUCTS— 

PLATES. 

SECTION I. 

PREPARATION OF THE STEEL FOR ROLLING FINISHED PRODUCTS. 

Reheating: While a few finished steel articles, such as plates, large 
rails and heavy shapes, which on account of their large mass retain their 
heat for a considerable length of time, may be rolled by rapid methods 
directly from the ingot without reheating, the majority of articles are so 
small that their temperature would fall far below the rolling range before 
the great amount of reduction required could be accomplished. For all such 
articles a reheating of the bloom, billet, or slab is a necessary step pre¬ 
liminary to rolling. Needless to say, this reheating of the steel is a matter of 
great importance and requires even more care than the heating of ingots. 
Compared with hot ingots the nature of heating is very different, for here all 
the heat is conducted toward the center from the surfaces exposed to it; 
and since in practice it is well nigh impossible to expose all surfaces equally 
to the heating medium, imeven heating is likely to occur, the result of which 
is a variation in the dimensions of the finished section. Here, too, as with 
ingots, the danger of burning or overheating is ever present. As the tem¬ 
peratures attained are far above the critical range, the reheating tends to 
undo the refining of the previous rolling. Since the extent of this obliter¬ 
ation of the original structure is about in proportion to the temperature 
above the critical attained it is desirable to keep the reheating temper¬ 
ature as low as possible, and to finish the rolling as near the critical range 
as practicable. However, some finished materials are so light that the 
highest temperatures attainable without injury to the steel are barely 
sufficient to complete the rolling, and in addition the wear-and-tear on the 
mills incident to rolling at the lower temperatures increases so rapidly as 
to add very much to the expense of rolling. Again, the surface of the 
metal is oxidized very rapidly in a flame or a hot atmosphere even slightly 
oxidizing, and this oxidation results in the formation of an insulating coat of 
scale that retards the heating. This scale may cause trouble in other ways, 
also, because, at the temperature which it is often necessary to maintain in 
the furnace in order to heat the steel to the proper temperature for rolling, 





REHEATING FOR ROLLING 


419 


it becomes pasty or quite fluid, and blooms or billets in contact in the furnace 
are often cemented together by it. Besides, the surface of the piece, 
being covered with this pasty scale, is liable to cause pieces of brick, sand, 
or other foreign substances to adhere to it, and these, being rolled into 
the steel, produce serious surface defects in the finished material, some of 
which are known as scabs, brick spots, pitted surfaces, etc. The loss of 
metal due to the formation of scale will sometimes amount to as much as 
5% and is seldom under 2%. 

Types of Reheating Furnaces: Reheating furnaces cannot as yet be 
said to have reached a standard in design and construction. They are, 
therefore, of various forms and types, and each furnace is constructed along 
lines which were thought to be the best suited to the local conditions at 
the time of its erection. Most of these furnaces are, however, of the 
reverberatory type, and may be fired with coal, gas, tar or oil, though 
the gaseous fuels are much preferred for this purpose on account of the ease 
with wdiich the temperature may be regulated. In order to conserve the 
heat as much as possible, they may be provided with waste heat boilers 
or be constructed on the regenerative or recuperative principles. New 
mills, however, the majority of wdiich are being electrically driven, cannot 
employ the waste heat boilers. The more modern furnaces are, then, 
built either on the regenerative or the recuperative principle, in both of 
which gaseous or liquid fuels or pulverized coal are used. 

The Regenerative Reheating Furnace is similar in working principle 
to an open hearth steel furnace. Gas and air ports at each end of the 
furnace are connected by flues that lead to checker chambers, made of the 
proper refractory materials for retaining the heat from waste gases and 
giving up the same to ingoing air, or air and gas if producer gas is used, 
the current being reversed at certain intervals of time. Unlike the open 
hearth furnace, however, the checker work for these furnaces is usually 
placed under the furnace, and, instead of the basin-like hearth, the reheating 
furnace is provided with a floor practically on a level with the door sills. 
A low bridge wall, which separates this floor from the up-and-down takes, 
forms a kind of combustion chamber and prevents the flame from impinging 
directly upon the steel. Above this combustion chamber the roof of the 
furnace slopes downward toward the middle of the furnace and reverberates 
the heat of the flame upon the floor. The steel is charged through lifting 
doors in one side of the furnace, and it may be drawn either through these 
same doors or through doors in the opposite side. Originally, it was the 
general practice to line the bottom of these furnaces with refractory siliceous 
sand, hence they are often called sand bottom furnaces. As the scale in 
melting unites with this sand to form a slag of a too high per cent, of silica 
to be used economically, these furnaces are now made up of magnesite or 
cinder, which, melted into place, makes it possible to use the resulting 
cinder in the open-hearth or blast furnace. These furnaces are used mainly 




420 ROLLING FINISHED PRODUCTS 





Fia. 72. Regenerative Reheating Furnace. 










































































































































































































































































































































REHEATING FURNACES 


421 


for reheating heavy material, such as blooms, slabs, and the larger billets, 
for which purpose they are very well adapted. 

The Recuperative or “Continuous” Furnace works upon the principle 
of counter-currents throughout. The combustion chamber is located at 
one end of the furnace, where the heated steel is drawn, while the chamber 
for recovery of the waste heat is located at the opposite end, which is 
always nearest the stack and where the steel is charged. In one current, 
the hot gases and flame from the combustion chamber are drawn by the 
chimney draft over the floor, which is separated from the combustion 
chamber by a bridge wall, and then downward through a series of spaced 
iron pipes to the stack flue. In the other current the course of the steel 
and the air for combustion run counter-current to the heat, the steel over 
the floor of the furnace, the air through the enclosed space about the hot 
pipes and a flue under the floor to the combustion chamber. The passage 
of all may, therefore, be made continuous, hence the name, continuous 
furnace. It will be observed that the billets move from the coldest part 
of the furnace to the hottest part, hence they are heated very gradually, 
reaching the rolling temperature just prior to drawing. The scale, there¬ 
fore, does not melt, and no slag is formed in the continuous furnace if it is 
fired with gas, oil or tar. When powdered coal is used for fuel, the silicious 
ash unites with the scale to form an easily fused slag that collects at the 
discharge end of the furnace. In order to push the billets through the 
furnace suitable pushing devices must be provided, and to aid in this work 
the floor of the furnace is sometimes inclined, sloping downward from the 
charging to the drawing end. To prevent the tearing up of the floor, skids 
for supporting the billets are provided, built into the bottom. These skids 
are generally made of heavy pipe through which a stream of water flows to 
keep them cool. An objectionable feature in the use of the skids is that 
they cause cold spots in the steel where the billets rest upon them. To 
overcome this defect the pipes are bent or off-set at the lower ends, or the 
billets may be delivered from the skids to a section of the bottom lined 
with magnesite. In this way the temperature of the cold spots is restored 
to near that of the rest of the billet. 

The Advantages of Continuous Reheating Furnaces are numerous. 
In the first place, they are the best type of furnace to precede a continuous 
mill. The use of complicated charging and drawing machines is avoided. 
The heating, being confined to one end of the furnace, makes it easy to 
regulate the temperature to suit the different grades of steel, and to heat 
to the rolling temperature only those billets that are to be used at once. 
Where the billets used are of constant length, the width of the furnace is 
so proportioned to the length of billet that the entire bottom is covered 
with the steel to be heated. Thus, there are no vacant areas on the bottom 
to decrease the heating efficiency of the furnace. The accompanying 
prints are intended to show the chief features in the modern constiuction 
of these two types of furnaces. 



422 


ROLLING FINISHED PRODUCTS 





\ 



































































































































































































































































































































SHEARED PLATE 


423 


SECTION II. 

THE ROLLING OF SHEARED PLATES. 

Methods of Rolling Plates: As previously indicated, plates may be 
rolled either from ingots or from slabs, and on several different types of 
mills. Thus, in England, and a few places in this country, Birmingham, 
for example, plates are rolled on a two-high reversing mill consisting of a 
train of two stands of plain rolls. In these mills, the stand nearer the engine 
has both rolls driven and is used for roughing, while the second stand is 
used for finishing and has, therefore, only the bottom roll driven. In the 
majority of these mills the ro’lls are run hot, that is, no attempt is made to 
cool the rolls during the rolling. In America the practice for rolling plates 
is entirely different. In all cases the rolls are kept cold by directing streams 
or sprays of water upon them during the rolling, and two types of mill, 
neither of which is like the English mills, are used. One of these, the 
universal mill, has already been mentioned, and will be described more in 
detail later, while the other, the invention of Mr. B. C. Lauth, of Pitts¬ 
burgh, is a kind of three-high mill. In this mill the top and bottom rolls 
are driven, are of the same size, and of large diameters, while the middle 
roll is friction driven and, in diameter, is usually about two-thirds the size 
of the other two rolls. The maximum size of the middle roll is determined 
by the width of the housing windows, as the roll is removed by passing it 
endways through this opening. The top roll can be raised and lowered in 
the housing, and the middle roll, through suitable levers hydraulically or 
electrically operated, can be brought into contact alternately with the top 
and bottom rolls, which then play the part of re-enforcing rolls. Thus, in 
making the bottom pass, the plate passes between this middle roll and the 
bottom roll, while the top roll is used as a re-enforcing roll. On the return 
pass, the middle roll is dropped down upon the bottom roll, and the piece, 
having been raised to the proper level by a tilting table, passes between the 
top and middle rolls. In either case, the amount of draught is controlled by 
screw downs acting against the top roll' in a manner somewhat like that 
of the blooming mill. The advantage of this construction will become 
apparent as this study advances. Plates rolled on this mill must be sheared 
on all edges, hence they are called “sheared plates’ ’ to distinguish them 
from universal mill plates which are sheared only on the ends to obtain 
the lengths required. The size of the sheared plate mill is determined by 
the length of the bodies of its rolls, while universal mills are distinguished 
by the maximum spread of the vertical rolls. 

The One Hundred Forty Inch Mill at Homestead as an Example of 
a Sheared Plate Mill: In this mill the top and bottom rolls, which must 
be carefully matched and of exactly the same diameter, are each approxi¬ 
mately thirty-eight and three-fourths inches in diameter when new, and 




424 ROLLING FINISHED PRODUCTS 


the middle roll twenty-two inches. All three are chilled rolls, the depth 
of the chill being between one and one and one-half inches. The bottom 
roll is held in place by bottom and side bearings of brass, which are fitted 
into the bottom of the cast steel housings. For the top roll, which requires 
both top and bottom as well as side bearings, riders for containing the 
brasses are provided. This roll is supported from below by steel-yard rods 
which extend from the bottom rider to the shorter arms of counterbalanced 
levers in the pits beneath the mill. In this respect as well as in the method 
of screwing down the top roll, the construction of the mill resembles the 
forty-inch mill at Duquesne. For driving the screws, however, a 60 h. p. 
motor is provided, instead of the hydraulic cylinder, and is connected to 
the screws through a worm shaft and crown gear. For indicating the 
draught on the mill a large drum or cylinder, about four feet in diameter 
and with an altitude equal to the total lift of the mill, is mounted on the 
top of one of the screws. The surface of this cylinder is divided vertically 
into parallel spaces, the width of which equals the pitch of the screws, one 
and one-quarter inches. The circumference of each circle separating a pair 
of spaces is then divided by vertical lines into a number of equal parts. 
By means of this arrangement and a stationary pointer, mounted on the 
housing beside the cylinder and set to point at zero on the drum when all 
the rolls are in contact and screwed down tight, the distance between the 
rolls may be read off direct and with great accuracy. For holding the 
middle roll in place, bearing boxes with side bearings which fit into chocks 
placed on the side of the housing windows are provided. For keeping 
this roll in line, liners are employed, and for raising and lowering it, a rest 
bar built on the plan of a swinging lever is fitted over each neck outside 
of the housing and across the window. One end of each rest bar is supported 
at an almost constant level by means of a turn buckle rod hung from the 
top of the housing, while the opposite end is connected to the plunger of 
a hydraulic cylinder which, located in the pit beneath the housings, furnishes 
the power for raising and lowering the roll. In many cases this cylinder 
is located on top of the housings, and in the most recently constructed mills, 
electric motors are employed instead of the hydraulic cylinder. 

The Drive and Connections: The top and bottom rolls are connected 
to the pinions through coupling boxes and spindles similar to those in the 
blooming mill. The spindles are eleven feet long, and both are supported at 
their centers by suitable bearings. The saddle box for the vibrating 
spindle is attached at one end to the pinion housing and at the other to 
the roll bearing box, thus keeping the motion of the saddle and spindle 
co-incident with that of the top roll. Since the middle roll of the mill is 
friction driven, the middle pinion is used as a driving pinion only, and is 
smaller than the top and bottom ones, the speed ratio being 11 to 19. The 
pinions are of the helical toothed type and are held in cast steel housings. 
A short spindle, four feet eleven inches long, connects the middle pinion to 
the driving shaft of the engine on which is mounted the fly wheel. This 



SHEARED PLATE 


425 


mill is driven by a 42" x 66" x 60" tandem compound engine, capable of 
giving 3500 h. p. at the speed of 64 r. p. m. Nearly all the new mills built 
since 1916 are electrically driven. The new one hundred ten inch mill at 
Homestead, otherwise known as the Liberty mill, is so driven. This motor 
was built and installed by the General Electric Co. It is designed to 
develop 4000 h. p. and to give a speed of 82 r. p. m. on full load. It uses 
alternating 3-phase current with a frequency of 25 cycles per second and a 
pressure of 6600 volts. The installation is marked for its simplicity; the 
peak loads are taken care of by means of a 55-ton fly wheel mounted on 
the same shaft with the motor. 

Difficulties in Rolling Sheared Plates: While the rolling of plate 
may appear to the novice as one of the simplest of rolling operations, yet 
there are problems connected with the rolling of wide plate that require 
the combined skill and experience of the heater, the millwright, the roller, 
and roll designer to overcome. If the slabs are not heated uniformly in 
all parts, the plates will curl and buckle in rolling, while a similar effect 
is produced if the rolls are even slightly out of alignment. The stretch 
of the housings and the stoving up of the screw are minor considerations 
in overcoming the difficulties of rolling exactly to gauge. The wearing 
away of the rolls, which in actual operation, takes place faster in the middle 
portions than at the ends, causes them to become hollow in a short time so 
that the plate is thicker in the middle than at the edges. Since the pressure 
for rolling must be applied at the ends of the rolls, this effect is increased 
by the bending of the rolls. The opposite effect would be produced if the 
rolls should become hot in the middle, the expansion causing an increase in 
their diameters. This last complication is avoided by keeping the rolls cold 
with water sprays above them. This water, running down upon the plate, 
has a tendency to cool it faster, but this cooling is not as rapid as might 
be expected, because the water assumes the spheroidal state on striking 
the very hot plate and glides off without being vaporized to any great 
extent. At the one hundred forty inch mill, the spring and wear in the 
rolls are provided for in the following manner: To remove the effects of wear 
the top and bottom rolls are dressed down every Saturday,either in position 
by attaching an electrically driven reduction gear to the driving pinion, 
which virtually converts the mill into a lathe, or by removing them and 
sending them to be lathe turned in the machine shop. To neutralize the 
spring in the rolls the middle roll is turned so that its diameter at the middle 
is a little greater than that at the ends. If this swell or belly in the roll 
were made to fit the top and bottom rolls it would almost represent an 
arc of a very large circle, but as it is impossible to dress the roll in this 
way, the lines are cut only approximately correct by tapering the ends and 
leaving the central portion of the roll cylindrical in form. The amount of 
the taper will vary with the hollowness of the mill, but is never less than 



42G. 


ROLLING FINISHED PRODUCTS 


one sixty-fourth nor greater than three sixty-fourths of an inch, thus making 
the difference in diameter between the ends and the center vary from one- 
thirty-second to three-thirty-seconds of an inch. The distance from the 
end of the roll to which the taper extends may vary from forty-six to fifty- 
six inches, thus making the central cylindrical portion twenty-eight to 
forty-eight inches long, and depends upon the width of plate being rolled. 
It is the practice, when advantageous, to roll the wide plates at the begin¬ 
ning of the week, while the mill is full, and to roll the narrower plates at 
the end of the week when the rolls have been worn down, and the hollow¬ 
ness of the mill is more pronounced. Even with these changes the mill 
will often become so hollow that it is necessary to roll the edges a little 
below gauge in order to get the weight correct. Hollowness in the mill 
tends to make the edges of the plate dovetail or buckle. During the week 
the middle roll will be changed four to six times. 

The Rolling Process on this mill, as on the English mill, may be looked 
upon as being performed in two steps or stages, namely, a roughing or 
breaking down stage and a finishing stage. In the breaking down of the 
slab the most important feature of the rolling is the determination of the 
draughts, the size of slab and the spring of the rolls being the controlling 
factors in this regard. With a heavy slab, that is, one six to ten inches 
thick, a maximum draft, or bite, of about three-fourths inch is possible. 
The amount of bite decreases as the slab thickness decreases and the width 
increases. The greater the surface the less the possible draught on account 
of the greater amount of work necessary in rolling. Following the first 
few passes the draughts become smaller and smaller because of the increased 
work required and also to allow material for the finishing. At least one- 
fourth inch is allowed for the finishing passes, as this amount is required 
to give sufficient material with which to remove the effect produced by 
the spring of the rolls. Were the spring not removed, that is if the plates 
were finished by a continuance of passes carrying the heavy draughts, the 
middle of the resulting plates would be much heavier than the sides. By 
decreasing the draughts the “spring” is removed, and the plate approaches 
nearer the desired weight and gauge. Blind passes, that is, passes in which 
no additional pressure is applied to the rolls, are also used in finishing for 
the same reason. The heavier gauge plates cause less spring in the roll, 
and fewer finishing passes are necessary, while with light gauge plates, 
especially on a full mill, it is necessary to start the finishing when about 
one-half inch above the final gauge, since a bigger draught is necessary to 
hold the plate and prevent buckling. Near the beginning of the rolling, 
the slabs are passed through the mill transversely a few times to obtain 
the desired width and are then rolled longitudinally. In gauging the width 
six inches are allowed for shrinkage, shearing, etc., on plate not over eighty- 
five inches wide, while seven to eight inches are allowed on plate from 




SHEARED PLATE 


427 


ninety inches to the maximum of a hundred thirty-two inches. Extra 
allowance on the wide plates is necessary to take care of the overlap, or 
lamination, of the top and bottom sides due to the greater flowing of the 
metal on these faces during rolling. Any large variation in the distance 
between the rolls from end to end shows up in the plate at once, since under 
such conditions it will curve to the side on which there is the less draught. 
If the variation is small it may not show up in this way. The plates are 
gauged four times daily at the edges and in the middle to determine the 
hollowness and variation. Excessive hollowness is corrected by putting in 
a new middle roll, while variations are overcome by inserting or removing 
liners under the bearing boxes. During the rolling, scale is removed with 
salt on common steels or with burlap and coal on nickel steel, as in the 
rolling of slabs. 

Cooling and Straightening: In order to keep the cooling of plate 
uniform, the roll tables are preferably provided with collared, or disc rolls 
instead of plain ones, which cause black streaks to appear across the plate. 
Disc rollers in the tilting tables of the mill also make it possible to roll 
very narrow slabs. These slabs are difficult to handle on plain rolls, because 
they do not ride these rolls in a horizontal position, but tend to fall down 
between them edgewise. This difficulty is overcome with the disc rollers, 
for by alternating the discs the bearing surface from roll to roll is brought 
nearer together than is possible with plain rolls, and there is no straight 
line of separation between rollers. After the rolling is completed, the 
plate is passed by roll tables to a Hilles & Jones cold roll straightener. 
This straightener is constructed of two rows, one above the other, of small 
rolls, five in the top and four in the bottom row. The centers of the rolls 
in the top and bottom rows are alternated, so that the piece, on entering 
between the rolls, is given a long bend or sweep which is then removed by 
smaller sweeps until the piece, on passing out of the rolls, is quite or nearly 
straight. Two or more passes may be required to straighten some plates. 
The best work is done on plates about one-half inch thick, as they still 
retain enough heat when arriving at the cold rolls to be well and easily 
straightened. The rolls are operated by motors, and the draught is set on 
the mill by gears connected to a motor. From the rolling order sheets, the 
cold roller obtains the gauge of the plate when finished and then sets the 
cold rolls to take a plate of that gauge. 

Laying-out and Stamping: After being straightened, the plates pass 
to the cooling bed and then to the marking tables. Here the heat number, 
slab number, customer’s name, or mark, and plate dimensions are written 
on the plate by the marker. The plate is now ready to be laid out by the 
gauger. Laying out consists of drawing out in chalk the plate or plates 
as they are to be sheared, it being remembered that the plate as rolled 
from a slab may be made up so as to give material for two or more plates, 
in which case the plate as rolled is called a combination. As the plates 





428 


ROLLING FINISHED PRODUCTS 


are still hot when gauged, allowance must be made for shrinkage, this 
allowance amounting to one-fourth inch in width and length for each hundred 
inches on plates up to one-fourth inch in thickness, and three-eighth inch 
for each hundred inches of length or width on gauges over one-fourth inch. 
This difference is necessary on account of the higher finishing temperature 
of the thicker plates. In case plates come to the marking table that will 
not make the plates ordered, on accoimt of being too short or too narrow, 
the material must either be applied on another order or put in stock. Any 
plates with objectionable surface defects are rejected at the marking table 
and stocked. Plates stocked at the table are treated in the same manner as 
rejections, although they are not listed as such, because they have not been 
finished at the time of stocking. If a plate has a snake or is pitted on one 
end. this part may be sheared off and the remainder used on a different 
order than that for which it was intended. Plates that are too narrow to 
make the ordered plates are held until an order can be found calling for such a 
gauge, width and length as can be cut from them. It is a duty of the stock 
marker to replace such plates as are taken from the marking table. A 
report is made on the rolling order sheet, by the marker, of the number 
of plates made on an order, and the stock marker informs the office of all 
plates made from stocked material. While plates are being laid out they 
are stamped, giving heat number or slab number as is desired, and any 
other stamp that may be called for on the order by the purchaser. Heat 
number, slab number and size is also painted on the plates with white lead 
after they are marked. Some orders require that heat numbers, etc., are 
to be painted instead of being stamped, this being more generally the case 
on very light gauge plates. The method used in laying out a plate can be 
described from sketches, such as those shown in Fig. 74. 

First, the width of the plate is taken at AB to determine the amount 
of stock over that of the ordered width plus allowance for shrinkage. The 
stock is then divided so as to give one-half to each side. Point C is set 
leaving the distance BC as excess stock. Point O is now set along XY 
in the same manner as point C. Line CO is drawn with a chalked string 
or a straight edge. Widths OM—EN—CP and others, if needed, are 
measured using line CO as a base. Line PM is then drawn by “the line 
drawer.” A right angled square is now used to draw line CP at right 
angles to CO, thus squaring up the plate. The true length of the plate 
is taken along CO, using C as a starting point, and OM is likewise 
drawn at right angles to CO. 

In case the plate is curved, the base lines must take the direction 
indicated in Sketch II in order to avoid scrap, and in case the length of 
the plate ordered is such as X'Y' the plate cannot be made on account of 
the curve. This plate must be applied on orders that require lengths of 
approximately XI and QR, with widths and gauge such as can be obtained 
on the given plate. Whenever the number of plates ordered to the same 




SHEARED PLATES 


429 


dimensions will justify the expense, patterns of wood are made for laying 
out. Sketch plates are always marked out to a templet, or pattern. 

Test Pieces: In laying out the plate sufficient material must be given 
to allow for the test pieces that are required. On sheared plates both 
longitudinal and transverse test pieces are often taken. 

Shearing: Three shears, one end and two side shears, are used on the 
one hundred forty inch mill, and are so arranged that the plate does not 
require turning to shear the sides. The ends are sheared first, and the 



plate is then passed over castors to the side shears. This mill is also 
equipped with a rotary shear for heads and other circular plates, an alligator 
shear and a scrap shear. 


























430 


ROLLING FINISHED PRODUCTS 


Shearing Tolerances: It is evident, even to the casual observer, that 
conditions at the mills are such that shearing to exact dimensions is imposs¬ 
ible. Observations made on any one mill will reveal many of these un¬ 
favorable conditions and also show that it is impossible to remedy them. 
The plates must be sheared in the order they are rolled, and, to keep up 
with the mill, rapid working is required, a condition that makes it difficult 
to lay out or shear accurately. Owing to variations in the thickness of the 
plates and in the time required for rolling them, they leave the cooling 
beds at widely varying temperatures. Since there is no way of knowing 
accurately just what this temperature is at the time of laying out the plate, 
proper allowance cannot be made for'the shrinkage, the total amount of 
which w r ill also vary with the dimensions of the plate. Thus, while a plate 
inch thick and 100 inches long may require an allowance of inch 
for length, a plate one inch thick and 200 inches long may require an 
allowance of % inch. Finally, since no mechanical stops can be used on 
plate shears, the plates must be adjusted to position under the shear knife 
by eye-and-hand methods, which are not favorable to accurate work. Since 
the conditions in the different mills, such as length and type of cooling bed, 
kind of material rolled, etc., vary a great deal, it is practically impossible 
to fix standard variations covering all kinds of plates that will be just to 
the mills and the consumers alike. In justice to the former it should be 
stated that every attempt is made to shear as near to the exact dimensions 
ordered as the class of material would appear to call for and the mill 
conditions will permit. 

Inspection for Size: After the shearing, all plates are inspected for 
size. If a plate does not measure up to the dimensions ordered or to within 
the tolerances permitted by the order department, it is rejected and return¬ 
ed to be applied on another order calling for the same grade of material. 

Weighers: All plates are weighed separately, the weight and number 
of plates made being recorded on a copy of the rolling order sheet given 
to the weigher. 

Checkers: The checker receives a copy of all rolling orders and checks 
each item for size and pieces ordered. On the weigher’s copy of the rolling 
order, he lists the estimated weight of the plate as ordered so as to give 
the weigher the ordered weight, who, after taking the actual weight, can 
determine at once whether the plate will meet the specifications as to 
weight. The checker lists all plates ordered in the order book, and receives 
a copy of all orders to be rolled on the mill, so as to avoid the making of 
duplicates in case a plate is ordered twice. In case error is found in dimen¬ 
sions of plates listed on the rolling order, the checker informs the roller 
and marker. The checker also lists all plates made in the order book, 
thus keeping a record of the plates still on order. 




UNIVERSAL MILL PLATE 


431 


Slip Maker: The slip-maker’s duty is to make a form giving the 
following information: mill, slip number, customer’s name, Carnegie order 
number, sheet number of order, heat number, number pieces made, dimen¬ 
sions, marks and actual weight. The dimensions, etc., are to be taken from 
the plate, formerly painted on by the painter at the marking table. A 
copy of the rolling order is at the disposal of the slipmaker to aid in identi¬ 
fying plates, but data cannot be taken from the order without seeing the 
marks on the plate, in as much as certain plates may, at the marking tables, 
be applied on orders different from those they were originally intended for. 
A new or separate slip is made out for each order number. The signature 
of the slipmaker is required on each slip for identification. 

Recorder: The duty of the recorder is to test the weights of all plates 
made and note the turn on which they were rolled and sheared. The 
record here taken is the final record of the product made and must be 
taken very accurately. Special forms are used for recording, showing turn, 
numbers, weight, descriptions of plates, etc. Special sheets are made for 
alloy steels and small pieces that are inspected at the time of measuring 
for size. 


SECTION III. 

UNIVERSAL MILL PLATES. 

The Forty=eight Inch Mill at Homestead as an Example of Universal 
Plate Mills: This mill consists of two horizontal rolls and four vertical 
rolls, two on each side of the horizontal ones, all contained in the same 
housings and driven by the same engine. This construction makes the mill 
a very complicated piece of machinery, a detailed description of which 
would be too lengthy to attempt here, so only such matters as are necessary 
to an understanding of the working of the mill will be discussed. While the 
working surface of the horizontal rolls is only four feet, which is the same 
as the maximum spread of the vertical rolls, the total length of the rolls 
is thirteen feet one inch, of which length twenty-four inches makes up the 
wobblers, forty-five inches the necks, and forty inches, twenty inches on 
each side, crosses the spaces in front of the vertical rolls, which must stand 
between the housings. These rolls are connected to the engine and are driven 
in the same way as the ordinary reversing mill. The total lift of the hori¬ 
zontal rolls is twenty inches. The screw down on these rolls is the same 
as that on the sheared plate mill, and the same form of graduated drum is 
used to indicate the lift of the rolls, or the gauge of the plate. The vertical 
rolls, whose centers are located three feet one inch from the centers of the 
horizontal rolls, are seventeen and one-half inches in diameter at the body, 
and the height of their rolling surface is two feet four and one-eighth inches. 
They are provided with bearing boxes at both their tops and bottoms. A 
five inch collar on the upper end of the lower neck rides on a side bearing 



432 


ROLLING FINISHED PRODUCTS 


in the bottom box which furnishes the vertical support for the roll. A 
screw, bearing on a frame attached to the bearing boxes and actuated by 
an electric motor, furnishes the means by which the pressure for rolling is 
applied to these rolls; for spreading them hydraulic jacks are used. Large 
discs, graduated on their circumferences and mounted on the screws, indicate 
the spread of the vertical rolls. As already stated, these rolls are driven 
through a system of gears by the same engine that drives the horizontal 
rolls. Beginning with the engine, the power is transmitted to the horizontal 
rolls in the usual manner for reversing mills, while the drive for the vertical 
rolls is taken off the upper pinion. . Upon the prolongation of the outside 
bearing of this pinion, a second gear is keyed. This gear meshes with two 
idlers, one on either side, which in turn mesh -with gears mounted on the 
ends of the two drive shafts for the vertical rolls. These shafts then extend 
to and across the roll housings, where they are supported by suitable bear¬ 
ings. On the section of these shafts included between the roll housings are 
mounted four sliding miter gears which mesh into similar crown gears keyed 
to the tops of the rolls. Through these gears the peripheral speed of the 
vertical rolls is adjusted to equal the speed of the horizontal rolls, and 
never more. Hence, the vertical rolls may be used on the piece only on 
the entering side of the passes, because if the vertical rolls were used on 
the delivery of the plate the greater speed of the piece due to the elongation 
produced by the horizontal rolls would jam the material between the two 
sets of rolls. The rolling of the piece on the entering side is preferable to 
rolling on the delivery side, as then thin plates would tend to buckle or 
bow up in the center on applying pressure from the vertical rolls. These 
rolls cannot be brought closer together than tw r enty inches. Hence, the 
mill has a range in width of plates from twenty to forty-six inches. 

The Operation of Rolling: Rolling universal mill plates involves 
most of the difficulties of rolling sheared plates, and in addition there are 
several features, due to the vertical rolls, that are not peculiar to sheared 
plate mills. Thus the piece must always enter the mill at right ang] es to the 
horizontal rolls, as otherwise the action of the vertical rolls will cause the 
plate to buckle or curl or jam between the rolls. As the plates rolled on 
this mill are in very long lengths, the slightest variation in the spacing of the 
horizontal rolls shows up as a decided camber in the plate as it runs out 
on the table. To correct this defect, which is prone to occur on universal 
mills, a spanner block is placed under the screw down on the roller’s side 
of the mill. By means of a spanner bar and a sledge hammer, this block 
may be turned and the proper adjustment made on this end of the upper 
horizontal roll to cause the plate to roll straight. As to the draught and 
manipulation of the horizontal rolls, the plate is reduced in the same way 
as on the sheared plate mill. On the vertical rolls the greatest draughts 
are taken in the first few passes, the object being to reduce the piece to 
the desired width as quickly as possible, after which the pressure on the 
vertical rolls is just sufficient to hold the piece to width. This mill rolls 



UNIVERSAL MILL PLATE 


433 


many plates directly from the ingot. Ingots intended for this purpose are 
rectangular in section, being from one to two inches wider at the smaller 
end than the width of the plate desired. In beginning the rolling of these 
slab ingots the rollers prefer to have the small end enter the mill first, as 
in this way the suddenness of the pull on the mill is avoided and the draught 
can be more easily adjusted, but many plates are rolled with the butt end 
of the ingot entering first. The chief objection to rolling plates directly 
from ingots is that the pipe and central line of segregation is rolled into 
the plate, and in order to avoid it the scrapping of a large amount of 
finished material is necessary. 

Straightening. Marking and Shearing U. M. Plate: From the rolls, 
the plate is carried on live roller tables to the two cooling beds, which 
extend in opposite directions from both sides of the receiving table. Here 
any curve or camber is removed from the plates by clamping them tightly 
to a straight edge. The buckles thus produced on thg edges of the plate 
are then flattened out with wooden mallets. While the mill is provided 
with a machine straightener, similar to the one employed at the one hundred 
forty inch mill, it is seldom used, the general practice at universal plate 
mills being to straighten the plates in the manner described above. Every 
plate rolled on this mill has the name and letters “Carnegie, XL S. A.” 
rolled into it at intervening spaces of seven feet. While on the cooling beds 
the plates are marked off for length, the heat number is stamped on, and 
the slab number, size of plate, order number and the customer’s name is 
marked on with white paint. The plates then move on to the receiving 
tables, which carry them to shears, where the plates are cut to length. A 
large shear used for splitting plates is also provided. Unless otherwise 
specified, two longitudinal tests for the physical laboratory are taken for 
each order or on each heat of steel; one test is taken from the top of the 
ingot, and the other from the bottom. The weighing, recording, and in¬ 
spection of the plates are then conducted as for sheared plates. 

Advantages of Universal Mill Plates: While the effect of the one 
way rolling on Universal mill plates, as will be explained shortly, is such 
as to require care and discrimination in their use, they, nevertheless, 
possess certain advantages over sheared plates that make them more 
desirable for some purposes. First, the possibility of producing plates of 
great length with a rolled edge makes them available for many purposes, 
such as girder construction, for which sheared plates are not suitable. 
Second, the ability to roll to fairly exact widths reduces shearing costs to 
a minimum. Third, the rolled edge eliminates all costs to the purchaser 
for machining. As a fourth advantage the greater tonnages that these 
mills are capable of producing may be cited, because this tends to keep the 
first cost to the customer low. 

Physical Properties of Plates: The effect of rolling on the physical 
properties of steel is now generally recognized by the users of plates, and 




434 


ROLLING FINISHED PRODUCTS 


specifications are usually written accordingly. In a previous discussion of 
this subject it was made plain that the controlling factors during rolling 
are the amount of work done and the temperature above the critical at 
which the rolling is completed. To these there should now be added the 
manner in which the rolling is performed. Attention has been called to 
the different methods of rolling plates in the preceding description. It 
will be recalled that the plate may be rolled from the slab with one reheating 
or from the ingot direct without reheating. As to the difference in effect 
produced by these two methods, there is little data on the subject, but 
reasoning from the theoretical standpoint, there should be no difference, 
The abandonment of the method of rolling from the ingot is probably due 
to economic considerations rather than to any tendency of the method to 
produce defective material. Again, in the rolling of the slab or ingot it 
was pointed out that all the rolling may be in one direction only, or the 
plate may be rolled both transversely and longitudinally. Here a marked 
difference is observed to result from the two methods of rolling. For 
example, if a slab or ingot be rolled in one direction only and a longitudinal 
and transverse test piece be cut from the resulting plate, little difference 
in tensile strength will be observed in pulling the two tests, but a marked 
difference in ductility will be found. Thus, the longitudinal piece will give 
from 4% to 7% greater elongation than the transverse piece, and 10% to 
15% greater reduction in area. Concerning the amount of work and finish¬ 
ing temperature, the ductility is affected in a somewhat erratic way, 
while the tensile strength is increased by increased work and lower 
finishing temperatures. Thus, a thin plate will show a very appreciable 
increase in tensile strength over a thick one rolled from the same 
slab or ingot, and to obtain the same strength in plates of 
different thicknesses it is necessary to employ chemical control. The 
following table is intended to show approximately the variations in the 
carbon content, other metalloids being constant, that should be made to 
produce plates of uniform strength when varying in thickness as indicated. 

Table 57. Showing Variation of Carbon Content with the Thickness 
of Plates to Give the Same Strength. 


Thickness 

Carbon 

of Plate 

Required 

H " . 

.-12% 

K " . 

. 15% 

l A " .-. 

. .-.17% 

* A " . 

-- 18 % 

l"... 

...-19% 

1 w .-.-. 

. - . 20% 


Inspection of Plates for size and weight is made by mill inspectors, 
while inspection for surface and other defects are made either by mill or 
customer’s inspectors. Certain surface defects, as snakes and surface 











DEFECTS IN PLATES 


435 




marks, may do the plate no harm if they do not extend too deep into the 
metal, and may be ground out with any suitable device. For this purpose 
a movable electrical grinding wheel is employed. The rigidness of 
the inspection may be surmised from a glance at the inspector’s list of causes 
for rejection, which is here appended. Most of these reasons are self- 
explanatory, while others have already been discussed, so that no further 
explanation is required. 

Table 58. Defects for Which Plates are Rejected. 


Defects Acquired or Caused From 


The 

In 

In 

In Laying 

In 

From Many 

Ingot 

Heating 

Rolling 

Out 

Shearing 

Sources 

Blister 

Burnt 

Split 

Wrong " 

Scant 

Snake * 

Pipe 

Bricked 

Slivers 

Dimen- 

Bad Edge 

Seams 

Slivers 

Scabby 

Dished 

sions 

Crop end 

Test lost 

Seams 

Cinder spot 

Pitted 

Made 

Test piece 

Duplicate 



Scored 

wrong 

cut 

Broken 



Buckled 


Knifed 

Ground 



Over 



too deep 



weight. 



Cracked 



Under 



Tests are 



weight 



not within 



Over and 



specifica- 



under 



tion 



gauge 
Scale 
Cambered 
Laminated 
Roll 
marked 
Bad edge 






(Universal 

Mill 

Plates 

only) 



































436 


THE ROLLING OF SECTIONS 


CHAPTER VIII. 

THE ROLLING OF LARGE SECTIONS. 


SECTION I. 


RAILROAD RAILS. 

-1 


Development of Rail Manufacture: Dating from the invention of 

the steam locomotive, the railroad rail represents one of the first sections 
with which the rolling mill operators had to deal, as well as one of the 
most difficult and certainly the most important. The importance of the 
railroad as a factor in modern civilization and progress is recognized by 
all, and that the rail is a most vital part in railroad operations is just 
as evident. With the advancement in speed of travel and weight of 
loads carried, more and more has been required of the rail, until to-day 
no material is subjected to more severe punishment in service than the rail¬ 
road rail. Exposed to the weather at all times, it is subjected, under 
constantly varying conditions, to immense compression and bending stresses, 
shocks, vibrations, friction and wear. The form of the rail, then, should 
be such as will give the greatest transverse strength, provide abundance 
of metal for wear, present a wide base for fastening to the cross tie, and 
still, for the sake of economy, be of the lightest section possible. Now, it 
so happens, that the form that best meets all these requirements is the 
section known as the American Tee Rail. It also happens that this section 
was, in the early days of rolling mills, one of the most difficult sections 
to roll, mainly on account of the wide flange. The history of rail develop¬ 
ment as indicated in the sketches of Fig. 75 gives evidence of this fact. 






Thus, the first real departure made from the original strap rail of 1808 
was the chair rail of 1820. As the chair of this rail was expensive, an attempt 
was made in the section of 1831 to roll a rail with a wide and relatively 
heavy flange on the bottom to replace this chair. The difficulty of rolling 
the flange led to the better balanced bull head of 1837, the U-shape of 1844 
and the pear head rail of 1845. Then came the compound rail of 1856 and 
the form of 1860, which is the U-shape of 1844 with the lower parts closed 
in and welded to form the web. As neither of these forms proved service¬ 
able, a demand for more metal in the head for wear forced a final return 
in 1865-8 to the tee shape with wide thin flange. From this date the design 
of rolls, quality of material, and lay-out of the mills has gradually been 
improved until at the present time the American rail mills are not only 
producing the largest tonnage of the world but also rails of the best possible 
grade. 



RAILS 


437 


Methods of Rolling Rails: Rails were originally rolled on the pull¬ 
over mill, and then on the reversing mill, which in England is the type 
of mill still employed for this purpose. But in this country all rails are 
rolled on the three-high mill, which formerly was usually made up of a single 
train of three stands driven with one engine. With the increase in the size of 
the section, which has almost doubled in weight within the last quarter 
century, and the growing demand for larger quantities and better quality 
in the product, a more advantageous lay-out of the mills for handling this 


1808 

Strap Rail 
19 lbs. per yd. 



1820 

Birkenshaw Chair Rail 
25.8 lbs. per yd. 



1831 


Clarence Chair Rail 
33 lbs. per yd. 


Stevens’, (the 1st. T-rail) 
40.8 lbs. per yd. 




1837 

Lock’s (Bull Head) 
Rail, 58 lbs. per yd 





1844 

Evans’ 40 lb.U-Rail 
First Rail Rolled in 
United States. 


1845 

58 lb. Pear Head 
Rail, First T-rail 
Rolled in U. S. 


1856 

Compound Type of 
Rail, 60 lbs. per yd. 


1858 

P. R. R. Standard 
85 lbs. per yd. 




1860 

Closed-U Rail 



1868 _ 

Welch Design 
67 lbs. per yd. 
First Bess, Rail 
Rolled in U. S. 
(1865) similar 
to this 



1874 

Chanute Design 
60.3 lbs. per yd. 




P. H. Dudley Design P. R. R. Standard 
80.2 lbs. per yd. 100 lbs. per yd. 



1910 

C. R. R. of N. J. 
135 lbs. per yd. 


Fig. 75. Sketches of Rail Sections Illustrating the Evolution of the Railroad Rail 
in America. 


material became necessary. The more modern rail mills will, therefore, 
consist of two or three trains, each separately driven and made up of one 
or more stands of rolls, all so arranged that the rolling of the piece in any 
one stand is complete before it is passed to the next succeeding one. With 
this arrangement the output of the mill is greatly increased without much 
increase in the speed of the rolls, because different pieces may be rolling 
at different stages at the same time, and the turning of the piece between 
passes is avoided. As to the heating of the steel, rails may, as previously 

































438 


THE ROLLING OF SECTIONS 


stated, be rolled either from blooms that have been reheated after having 
been rolled from the ingot, or on the original heat of the ingot. The latter 
method, which was introduced a few years ago mainly to save the extra 
cost of reheating, was until very recently looked upon with favor both by 
the manufacturer and the consumer, who believed that the scheme would 
have a beneficial effect upon the quality of rail produced, due to the fact 
that the material was necessarily finished at a low temperature. Within 
the last two years, however, sentiment appears to have taken a swing in 
favor of reheating, because, as is claimed by the advocates of reheating, 
the increased speed of rolling combined with the heavy draughts required 
to complete the rolling on the original heat is liable to produce a condition 
favorable to the formation of fractures. The effects of too rapid reduction 
have already been discussed. For the same reason the temperature of the 
ingot is kept high, which fact increases the danger of overheating. In 
addition, the difficulty of keeping the finishing temperature constant, pre¬ 
sents a serious problem. On the other hand, by reheating the bloom the 
two initial rolling temperatures may be lower and be kept more uniform, 
and the shaping of the rail may progress more leisurely. As to the manner 
of forming the section, there are two methods of rolling, known as the flat, 
or slab-and-edging, and the diagonal, or angular, method. To impart even 
a slight understanding of these methods requires a lengthy explanation; 
but in the proper design of the various passes for the progressive forming 
of the rail, as for any section, lies the crux of the rolling process. Therefore, 
as the subject is one of great interest, an attempt is to be made to discuss 
the matter in as brief and comprehensive a manner as possible under the 
headings that follow. 

How to Study Roll Design: The best way to explain roll design is 
by an example, for it is as yet an art acquired mainly by experience. While 
subject to natural laws, the scientific aspects of the subject have not been 
fully developed, and the roll designer has few rules to learn. This con¬ 
dition tends toward individuality in designing, with the result that it is 
seldom two designers will be found to do the same thing in the same way. 
To serve as such an example the flat method of rolling as carried out at 
the Edgar Thomson Works will be described, because, of the two methods 
of rolling, this is the older and the one more generally employed. Before 
beginning with the example, however, some preliminary explanations are 
required. 

Precautions to be Observed in Designing the Rolls: Of course the 
first consideration in roll designing is to produce a finished piece of the 
correct size and form, and this must be done by spreading, bending and 
directing the flow of the steel. The ease with which this forming is done 
depends on the plasticity of the metal, which in turn is affected by the kind 
of steel, whether open-hearth or Bessemer; the grade, whether high or low 
carbon; and the temperature. With the speed of the rolls fixed, the tem¬ 
perature confined to a very narrow range, and the kind and grade of steel 



RAILS 


430 


given, the only instrumentality remaining in the hands of the roll designer 
is the size and shape of the passes, and in part of these, at least, the size 
will be governed by the size of the bloom. In designing the passes, a good 
designer will endeavor to work the steel in such a manner that the quality 
of the product will be benefited, and no defects will be developed. The 
defects that require constant care are fins, laps, overfills and underfills 
Laps may result from fins or a collaring of the piece in the rolls; overfills, 
from worn rolls, bad or improper design; and underfills either from bad 
design or incorrect adjustment of the rolls. 

Stages of Reduction: The formation of the rail from the bloom may 
be looked upon as taking place in three steps or stages. The first stage, 
called the roughing, is merely one of preparation; in it a large amount of 
work is done, but this work is expended mainly in reducing the size of the 
section and elongating the piece. At the Edgar Thomson Works the piece 
is reduced in seven to nine roughing passes. In the first four to six passes, 
rolling by the slab-and-edging method, the section retains the rectangular 
shape, while in the next three passes a little shaping of the flange is begun 
to prepare the piece for the first finishers, in which there are five passes. 
These passes are given names in order, indicative of the nature of the work 
they are intended to perform, as follows: slabber, first former, second 
former, third former, and the leader. The leader is the pass just previous 
to the finishing pass, which is located in a separately driven stand of two- 
high rolls. With this explanation of terms used, the different steps in the 
design of the rolls and the rolling may now be traced. They are as follows: 

The Section: No original designing of section is done by the roll 
designer. The first requirement in the rolling of a new section is, then, that 
the roll turner be supplied with a drawing or print of the section, which 
must be accompanied with all the dimensions, preferably indicated on the 
print. The weight of rail desired or expected should also be given. Here 
the matter of dimensions is of extreme importance, for the designing of the 
templets cannot be started until each and every dimension required is 
given. These dimensions not only include linear measurements, such as 
height of rail, width and thickness of parts, but radii of all curves, and 
amount of slope on inclined surfaces expressed in degrees or percentages. 

The Cold Templet: With all the necessary information before him, 
the first step taken by the roll designer is to prepare a drawing for the 
cold templet. This templet is made of brass and represents an exact section 
of the rail when cold. This drawing is constructed on the axis of symmetry 
of the rail, which is the vertical line drawn through the center of the head, 
of the web, and of the flange. On this line the section of rail is symmetrically 
constructed to the dimensions given on the drawing, all the dimensions 
being made with extreme care and accuracy. All measurements are made 
with micrometers or steel rules. If a rule is used a magnifying glass is 
employed to take the readings. The construction lines are made as fine as 
possible. Even the contraction and expansion of the drawing paper, due to 






440 


THE ROLLING OF SECTIONS 






the varying humidity of the atmosphere, is taken into consideration, and 
the proper allowances are made. With this very accurate drawing com¬ 
pleted, the area of the section is measured with a planimeter in order to 
check up the weight of the section.If this weight should differ from that 
given on the original print or drawing, the templet drawing is checked and, 
if correct, the customer is notified that the actual weight will not be as 
specified. No further work may then be done till this question of weight 
is settled, when the brass templet will be made from the drawing. 


, ) PaNUmplet Om wifvs 

l v 

' 


PASS 

HEAD 

WEB 

BASE 

TOTAL 

%RED. 

SPREAD 

FINISHING 

14.4 

5 4 

12.1 

31.9 

5% 

Vs" 

LEADER 

15.2 


12.7 

33.6 

5.7 

15% 

&" 

3rd FORM. 

17.9 

6.7 

14.9 

39.5 

20% 

3 // 

2nd FORM. 

22.4 

8.4 

18.6 

49.4 

32 

24% 

3 ff 

1st FORM. 

29.5 

11.1 

24.3 

64.9 

32 

22% 

3 ft 

SLABBER 

37.8 

14.2 

31.2 

83.2 

32 


Fig. 76. Pass Template Drawing—Slab-and-Edging 
Method of Rolling Rails. 


.a 

to 

D 

O 

Ph 


Jj 

<M 


bD 

a 

o 

Ph 


% Reduction in Passes. 


No. 

Pass 

— 

% Red. 

A 

Finishing Pass 

5. 

% 

B 

Leader 

15. 

% 

C 

3rd. Forming 

20. 

% 

D 

2nd. Forming 

24. 

% 

E 

1st. Forming 

22. 

% 

F 

Slabber 

23. 

% 

G 

9th. Pass 

24.5 

% 

H 

8th. “ 

24.5 

% 

I 

7th. “ 

22. 

% 

J 

6th. “ 

27. 

% 

K 

5th. “ 

22.8% 

L 

4th. “ 

17.1 

'% 

M 

3rd. “ 

28.8% 

N 

2nd. “ 

17. 

% 

0 

1st. “ 

14.5% 

P 

Bloom 



























































































































441 


ROLL DESIGN FOR RAILS 


The Hot Templet: The next step, which is really the first step in 
designing the roll passes, is the making of the hot templet. This templet 
is exactly like the cold templet, but larger in size to allow for contraction, 
as it represents the section of the rail at the finishing temperature of rolling. 
The co-efficient of contraction, or exact amount to allow here, is determined 
by experience. From this hot templet the various passes are designed 
successively as the experience and judgment of the designer dictates. 

The Pass Templet: In designing these templets, the designer con¬ 
structs each in a drawing showing the different passes superimposed upon 
each other as in the accompanying illustration. In actual practice these 
drawings are constructed full size, but for convenience in printing this 
photograph is three-eighths natural size. This illustration represents the 
passes for a light rail rolled by the slab-and-edging method. In this method, 
the axis of symmetry of the rail coincides with the pitch line and is parallel 
to the train line of the rolls, as can be seen from the print. The more darkly 
shaded area in the photograph represents the hot templet, with the pitch line 
or axis of symmetry drawn through it, and from it the grooves in the finishing 
pass are cut. From this pass the roll designer works back to the bloom. 
As a preliminary step toward designing these passes, a table like that shown 
attached to the photograph is prepared. In a vertical column, headed pass, 
are placed the names of the various passes from slabber to finishing, while 
the figures in the columns designated as head, web, and base represent 
the sectional area of the different passes for these parts expressed in pounds 
per yard, which is directly proportional to the area in square inches. This 
table is prepared as follows: The areas of the different parts of the rail 
are fixed by the hot templet. In this section the metal was proportioned 
in the design so as to give 14.4 pounds per yard in the head, 5.4 pounds 
per yard in the web and 12.1 pounds per yard in the flange, the total being 
31.9 pounds per yard, which is heavier than the cold section by 1.4 pounds 
per yard. This difference is due to the fact that the weight of the hot 
section is calculated as if it were cold, a correction for difference in gravity 
not being necessary for this purpose. Next will be put down under the 
column headed per cent, reduction, the amount of reduction expressed in 
per cent., which from experience and judgment, the designer thinks will 
be best. In this case these amounts are as follows: In the finishing pass 
one-thirty-second of an inch reduction on each side of the web is allowed 
for the marking; in the leader, 15%; in the third former, 20%; in the second 
former, 24%; in the first former, 22%; and in the slabber, 23%. From these 
figures the areas of the different parts of each pass are calculated, and the 
blanks in the table filled in as shown. Next, the amount to allow for spread 
of the piece from one pass to the other is decided upon and placed in the 
column headed spread. This allowance is expressed in fractions of an inch 
and is measured and allowed for along the axis of symmetry as shown by 
the positions of the rail heads in the photograph. With the reduction for 
the various passes and their parts thus apportioned, the designer then pro- 




442 


THE ROLLING OF SECTIONS 


ceeds to draw in the passes, as designated in the photograph by the letters 
a to p, and in doing so he keeps the following points constantly in mind. 
First, is the danger of forming fins. As an aid in avoiding these defects the 



FlG * Plaiw S e h0Win8 DifEerence in Peripheral Speed of the Rolls at Web, Head, and 


piece is passed through the mill so that each side of the pass alternately enters 
an open and closed side of the groove. How this is done on the three-high 
mill without turning the piece can be seen from a study of Fig. 78. Even 







































ROLL DESIGN FOR RAILS 


443 


with this arrangement fins would still be formed if the passes were not 
properly designed. To avoid all danger of fins two tricks of design are 
here resorted to. Thus, in the leader, or pass a, the corner of the head, 
which is to come opposite the openings between the rolls in the finishing 
pass, is well rounded off, so that the spread or flow of the metal will be 
taken up in filling out this rounded corner and none will remain to be forced 
into the clearance. For the same reason, that half of the flange on the 
same side of the rail is left much shorter. It will be observed that this 
provision is made in all the passes down to the slabber. From the photo¬ 
graph it will be noticed that most of the work from the slabber is done 
along the fishing of the rail, the metal being forced horizontally from the 
central portion of the slab toward the head and flange and vertically into 
the web. This is done by holding the working surface under the head 
and on top of the flange at the angles shown. In designing this part of 
these passes care must be taken to see that the line XY at the bottom 
of pass d , for example, is not greater than X'Y' at the top of its preceding 
pass c, as otherwise the piece would be collared when it entered d. Great 
care is necessary in distributing the reduction of each part to prevent the 
metal flowing away from parts where it is needed. Thus, for example, if 
a too great reduction in the web takes place in one pass, it will produce a flow 
of metal away from the head, causing the latter to be underfilled. The 
cause for much of the trouble of this kind lies in the different diameters 
of the pass, which causes a different roll speed for head, web andflange, 
and hence different rates of elongation. If the elongation at one point due 
to increased speed of the rolls, is not balanced by elongation produced through 
compression at the point of less speed, the section will be imperfectly 
formed, or cracks will result. The accompanying illustration (Fig. 77) will 
help in understanding this point. In all reduction, it is a good plan to keep 
the angle of bite well below the limiting angle of 30°. In the first roughers 
the difficulties of design are approximately the same as those of the three- 
high bloomer, and no further explanation of these passes is required. 

Preparation for the Rolling: After the passes have all been con¬ 
structed properly in the drawing, a set of working templets, including both 
male and female for the cold templet, is made from the drawings. The 
working templets may be of steel. These templets may number from the 
slabber down only, as the roll designer strives to keep the roughing passes 
of such shapes and sizes that the same set may be used for a large number 
of different sections of the same general design. When completed they go 
to the tool shop, where they are used as patterns in making a set of tools 
for turning the rolls for the section. For the last six passes, that is, number¬ 
ing from the slabber to the finishing, inclusive, twenty-two different tools 
are required for each type and size of rail. After shaping these tools to a 
little over size, they are tempered and then redressed to exact size before 
they can be used to turn the rolls. When ready, templets and tools pass to 
the roll shop, where the work of turning the rolls is done. Here the templets 






444 


THE ROLLING OF SECTIONS 



k. 


Roughing Stands. 















































































































































































































































































































































































































RAIL MILLS 


445 




Rolling Heavy Rails by the Slab-and-Edging Method. 


First Finishing Stand. Second Finishing Stand, 






































































































































































































































446 


THE ROLLING OF SECTIONS 


are used by the roll turner in cutting the grooves, which must be of the 
exact size and shape of the templets. At Edgar Thomson the roughing 
rolls are adamite or sand rolls, more often the latter; the second rougher, 
or former, are sand rolls; and the finishing are chilled rolls. 




Fig. 79. Plan Showing Arrangement of Rolls for Diagonal Rolling of Rails from Billets 









































































































































































































































































































































































RAIL MILLS 


447 


The Diagonal Method of rolling is represented on the accompanying 
cut of a light rail mill where this method is employed altogether. It 
differs from the slabbing method in that the shaping of the rail is begun 
with the first pass in the roughers and, instead of first compressing the 
bloom to a smaller size and then forming the section partly through com¬ 
pression and partly by spreading, the process is one of compression from 
beginning to end, as must be evident from observing the position of the 
piece in passing through the rolls. From a quality standpoint the method 
is thought to possess some advantage over the slabbing method by virtue 
of the fact that a greater amount of work is done on the tops of the head 
and flange, where it is needed. From the operator’s standpoint it would 
seem to have both advantages and disadvantages. As an instance of the 
former, it is pointed out that the angular grooves make it easier to redress 
the rolls and tend to give them a greater life, because the cuts to restore 
the section need not be so deep. To restore a section of the flat grooving, 
cuts as deep as one-half inch are usually required on smaller sections, while 
as much as three-fourths inch is needed on the larger ones. The chief 
disadvantage of using the method lies in the great side thrust of the rolls, 
which is very undesirable and difficult to provide for. It also requires more 
roll space than the flat method for the same number of passes. 

The Mills: There are four rail mills at the Edgar Thomson plant, 
but one of these, the oldest, is used exclusively for rolling sheet bar, billets, 
etc. Of the mills used for rolling rails, No. 1 mill is the older. It consists 
of three stands in tandem, each separately driven. The first roughing 
stand is driven by a 40" x 78" x 60" horizontal vertical compound con¬ 
densing engine, and the rolls are twenty-eight inches in diameter. The 
second stand, driven by a 50" x 78" x 60" tandem compound condensing 
engine, contains rolls twenty-seven and one-half inches in diameter. The 
finishing stand, which is two-high, is made up of rolls twenty-five and one- 
half inches in diameter, and is driven by a 32" x 56" x 48" tandem compound 
condensing engine. This mill, originally built for a twenty-four inch mill, 
is evidence of the rapid increase in the size of roll sections and the extremities 
the mills are put to in order to meet the demands made upon them for 
heavier rails. The mill now rolls rails from twenty-five pounds to one 
hundred poimds per yard. The No. 2 mill was completed in the early part 
of 1916 and is designed to roll rails up to one hundred fifty pounds per yard, 
which weight, it is hoped, will meet all demands for some years to come. 
Up to 1918 the largest section rolled was a hundred thirty poimd rail. In 
this mill all the rolls are thirty-two inches in diameter, when new. The 
pitch of the pinions is twenty-nine inches, which adapts the mill to rolls 
as small as twenty-eight inches in diameter. Like the No. 1 mill, the 
No. 2 is made up of three trains in tandem, but the first roughing train 
contains two stands in order to provide ample roll space for rolling laigc 
sections by either the flat or diagonal methods. The bodies of the rolls 
in the first three stands are sixtv-four inches in length, while in the 



448 


THE ROLLING OF SECTIONS 


finishing this dimension is reduced to forty inches. The first and second 
trains are driven by 50" x 78" x 60" tandem compound engines. The fly 
wheels on these engines weigh 100 tons each, and the speed of the engine 
is about 60 r. p. m. The third train is driven by a 44" x 74" x 54" 
horizontal vertical compound engine, which has a speed of 65 r. p. m. 
The first or roughing stands on each of these two mills are served by lifting 
tables, and the intermediate stands by tilting tables. The No. 3, an eighteen- 
inch mill, employs 19" x 42", 19" x 38" and 19" x 20" rolls, and rolls rails 
from twelve pounds to forty pounds per yard. It consists of two trains 
in tandem, each of two stands; number one and number three stands, both 
three-high, make up the first train, while number two, a three-high stand, 
and the two-high finishing stand are in the second train. Each train is 
independently driven by a 1500 h. p. electric motor. Rails rolled on these 
mills have distinguishing marks. Thus, heavy rails rolled on the No. 2 
mill have the sign, © , rolled on the web, and light rails rolled on the No. 1 
mill are distinguished by the sign, =, similarly located. 


Rolling Heavy Rails: After the rolls have been properly turned 
they are placed in the housing in their proper positions and carefully lined 
up. A trial rolling on a short bloom will then be made, and during this 
rolling the boss roller will watch the piece closely to see that it goes through 
the mill all right. If the section is a new one, the roll turner and designer 
will also be present to watch the trials. If the trial piece goes through 
the mill without causing trouble, a section is sawed, cooled, and examined 
by the roller and roll designer. In doing this, the piece thus rolled is gauged 
by means of the male and female templet which the designer has furnished 
the roller. If this section is found to be correct, the mill is then ready to 
begin the rolling, which is really the simplest part of the process. The roller 
watches the mill closely to see that everything is running right, and at 
frequent intervals will gauge and examine samples of the rails. In addition, 
he walks down to the cooling bed about every fifteen minutes to examine 
the rails for any defects that may be caused in the rolling, such as collar 
marks, underfills, roll marks, overfills, guide marks, cracks or seams. If 
he finds a defect in rolling, he hastens to make the necessary adjustments 
to correct the trouble. 

Unavoidable Variations: One of the things that carmot be avoided 
in the rolling is the wear of the rolls. While it occurs over the entire surface 
of the groove the parts of the groove subject to fastest wear are those 
which do the greatest work. Referring to the photograph of the drawing 
for the pass templets, it may be seen where the greatest wear will take 
place. This results in a decrease in the fishing of the rail as shown in the 
following sketch. It is also a difficult matter to keep the base perfectly 
flat, because the high collar in the finishing passes supporting this part of 
the rail tends to wear away the edges faster than at the bottom of the groove. 



STEPS IN SHAPING RAILS 


449 


The slight overfill that results produces the defect known as the rocking 
base, this wearing is very rapid, and with the mill running steadily, one 
dressing of the rolls lasts but from twenty-four to thirty-six hours. 



The Various Steps in Shaping of Rails: To trace the material from 
the ingot, the work begins at the forty-eight inch mill previously mentioned, 
where the very slow speed and relatively great reduction gives more of 
the pressing and less of the stretching effect of rolling, and is intended to avoid 
much of the danger of tearing or cracking the ingot. The large fillets used in 
the grooves keep the corners of the ingot well rounded. This mill, reducing 
the ingot from 233^" x 233^" to 153^" x 183^" leaves less work than usual 
to be done on the three-high bloomer which produces a 93^" x 93^" bloom. 
From the bloomer the long bloom passes to the shears where the proper 
discard, which is varied in different specifications, is made, and blooms of 
different lengths are cut to suit the conditions. Large rails are rolled two 











450 


THE ROLLING OF SECTIONS 


lengths to the bloom, while lighter ones may run into three lengths to the 
bloom. Leaving the shears,, the blooms travel on roll tables to a distri¬ 
buting point, where they are sent to No. 1 and No. 2 rail mill furnaces or 
to No. 4 billet and sheet bar mill. The furnaces serving the two large 
rail mills, which extend parallel to each other and are housed in the same 
building, are arranged in one row at right angles to the mills and in such 
a manner that the blooms may be charged on one side and drawn on the 
other which is nearer the mills. From the rolls the piece passes on to the 
saws, and then to the finishing and inspecting department. 

Cutting: For cutting rails four high speed (1500 r. p. m.) toothed 
circular saws are provided. The saws are mounted over the delivery table 
on the free ends of tilting arms, whose axes are concentric with the drive 
shafts. Belts then connect the saws with their driving shafts, which are 
electrically propelled. On No. 1 mill all the saws are mounted on one shaft 
which is driven by one motor, but in No. 2 mill each saw is mounted on a 
separate carriage and is driven by an individual motor. The tilting arms 
are electrically controlled so that all the saws may be made to cut simul¬ 
taneously. These saws are adjustable to cut different lengths from thirty 
to sixty feet, though thirty and thirty-three feet are standard lengths. In 
cutting the rails, proper allowance must be made for shrinkage, which is 
nearly three-sixteenths inch per foot, or about seven inches for a thirty- 
three foot, hundred pound rail. The exact amount of the shrinkage depends 
upon the temperature at which the rail is sawed, hence many railroads 
specify the amount of shrinkage per rail, and in so doing fix the finishing 
temperature of rolling. The allowance should be not less than one-fourth 
inch over or under length specified. Since the rails do not always leave 
the finishing rolls perfectly straight, it is not always possible to make a 
square cut, and one-thirty-second inch off-square should be allowed. Rails 
eighty-five pounds or over are rolled in double lengths, and on blooms on 
which tests are taken, six to eight feet is allowed for physical test pieces, 
which are cut from the ends of the piece. Smaller rails are rolled in triple 
lengths. Great care is required in adjusting the height of the saw blocks 
in order to avoid kinking or scratching the rail, and to secure a square cut. 
From the saws, the rails pass under a stamping machine, which marks the 
heat number and the position of the rail in the ingot, the latter being desig¬ 
nated by letters beginning with A at the top of the ingot. At Edgar Thom¬ 
son the A cut is discarded on all heavy rails. About sixty feet from the 
stamper is located the cambering machine which consists of a set of 
horizontal rolls with a vertical roll on each side, all in one housing, and set 
to bend the rail slightly so as to make the top surface of the rail convex 
from end to end. A scale located near the end of the delivery table is used 
for checking the weight of the rails as often as desired, before they are sent 
to the cooling beds. The No. 1 and No. 2 mills, being arranged parallel 
to each other, deliver their product to what may be considered a single 
large cooling bed, where the rails from both mills are slowly moved in one 
direction, which is toward the finishing room. 




FINISHING RAILS 


451 


Recording: A complete record is kept of all the steel rolled in the 
mills from the time it is made in the open hearth or Bessemer converter 
until it is shipped. This work is done by the recorder, who traces the 
material through the mills, and is so complete that it is easy to show, not 
only the kind of steel from which each rail is rolled, but the heat, the number 
of ingot, and its position in the ingot. At these mills the work of tracing 
the material is much facilitated by the use of an electric signalling system. 

Finishing and Inspection: The finishing room is arranged to the 
best advantage possible for handling the rails. In it are located the 
straightening and drilling machines (fourteen in number) in two rows parallel 
to each other and to the two mills, and extending in the same direction 
beginning at the mill side of the cooling beds. Between the row of 
straighteners and the cooling beds is a system of roll tables, which carry 
the rails from the beds and distribute them to the different straighteners. 
Here the rails are marked with a stamp to indicate the individual work¬ 
men responsible for this part of the work. The straightening machines, 
or gag presses, are provided with a bottom bed, on which the rail is 
supported at two points from below, and a top block which moves up and 
down between these two supporting lines with a fixed stroke of such length 
that the block will not touch the rail by about two inches at its lowest point. 
The block has a double face, each side of which is inclined toward the 
center line, where the faces cut each other. This form, combined with the 
different dimensions of the gag, a rectangular shaped block of steel which 
is inserted between the face of the block and the rail to be straightened, 
makes it possible to control the amount of bend that the rail receives and 
to adapt the machine to the different dimensions of a rail. For the different 
sizes of rails, the faces of the blocks are made adjustable by means of set¬ 
screws and liners, while for different sections different gags must be used. 
To straighten a rail, one workman is stationed in front of the machine and 
another at the end. By sighting along the rail, the man at the end locates 
the crooks in the rail and brings them under the blocks, while the man 
before the machine, acting under directions from the workman at the end, 
inserts the gag in such a way that the stroke of the machine will bend the 
rail enough to straighten it, which requires that the rail be bent beyond 
its elastic limit in order to give a permanent set. Next, the burrs made 
by the saws on the ends of the rails are cut off with chisels, and smoothed 
with a file. The rails are then given a preliminary inspection by an employee 
of the Company, in order to avoid unnecessary work being done on rails that 
may be rejected. As the inspection is completed, the rails are moved to the 
drilling machines, which are arranged in pairs and so spaced that, when one 
machine has completed the drilling on one end of the rail, it is moved under 
the other machine which drills the holes in the opposite end. These machines 
are each provided with three drilling spindles, the middle of which is fixed, 
and may be made to drill from one to three holes at one time. The rails 
are then moved sidewise through openings in the building to the inspection 





452 


THE ROLLING OF SECTIONS 


beds where they are walked, or inspected, both by a company’s inspector 
and by the customer’s, if so specified. The outside inspection covers mainly 
surface defects, such as seams, slivers, guide marks, and pits that may 
have been overlooked by the inside inspector, and the bolt holes. The 
rails, having been measured and gauged by the inside inspectors and rollers, 
the dimensions are checked only at intervals by the outside inspector. 
The location of the defects are marked with chalk. If these are located 
near the end, that portion of the rail may be sawed off and the rail still 
applied on the order as a short of first grade. Rails that fall below the 
allowance as to length are also disposed of in the same way. If the defects 
are many or near the center, the rail is either classed as a number two or 
sent back to the mills to be rolled into a light rail. In both the inside and 
outside inspection, the rails are walked twice, once with the base up, again 
with the heads up. As the rails are accepted by the inspectors, they are 
counted, the number being checked up with the original order. Then 
they are picked up by immense magnets attached to over head electric cranes 
and placed in the cars where, after weighing, they are ready for shipment. 

Light Rails: The rolling, finishing and inspection of light rails, as 
well as the material used, are somewhat different from the same operations 
for heavy rails. To begin with, the number three mill in which most of 
these rails are rolled, is operated as a separate unit, practically independent 
of the rest of the works, and with the exception of re-rollings from rejected 
heavy rails, all its product is rolled from billets which are obtained from 
other works. For this reason neither check analyses nor physical tests are 
made on light rails, because, even if such tests were made, there would be 
no way of indentifying the rail as having been made from the same steel from 
which the tests were taken nor of knowing that the tests represented the 
material in an order. The billets are heated in one of two continuous gas 
fired furnaces and are rolled by the angular method on six passes in the mill. 
Rerolled rails receive two additional passes in the first roughing stand, 
which is provided with tilting tables for the purpose. Leaving the rolls, 
the rails are sawed into lengths of thirty feet or under and are passed to the 
cooling beds. When sufficiently cold they receive a preliminary inspection, 
in which they are measured for length, and then passed through a roll 
straightener to punching machines where both bolt holes and bond holes 
are punched. Since the roll straighteners straighten the rail in one direction 
only and usually fail to produce a perfectly straight rail, even in one 
direction, gag presses are employed to complete the straightening. As for 
heavy rails, light rails are subject to a second, though less rigid, inspection 
after all work is completed. The mill is also equipped with cold saws, 
but cold sawing is undesirable, for it works a great hardship upon the mill, 
increasing the cost greatly, due to extra labor and scrap loss. For handling 
the rails a large gantry crane of an improved form which travels on tracks 
laid on the ground is provided. Light rails are weighed in cars before 
shipment. 




RAIL JOINTS 


453 



Continuous Rail Joint. 



Duquesne Rail Joint. 



Weber Rail Joint. 



100 Per Cent Rail Joint. 



Duquesne and 100 Per Cent Joint. 




Q & C Bonzano Rail Joint. 



Abbott Rail Joint. 



Fig. 81. Sketches Showing Different Kinds and Types of Rail Joints 











































































454 


THE ROLLING OF SECTIONS 



Continuous Insulated Rail Joints 


Weber Insulated Rail Joint 


Keystone Insulated Rail Joint 



Braddock Insulated Rail Joint 





O’Brien Insulated Rail Joint 

Fig. 82. Types of Insulating Rail Joints. 
The heavy black lines represent insulating fiber. 


SECTION II. 

THE SHAPING OF RAIL JOINTS. 

Rolling Rail Joints: Rail joints are made in so many different forms, 
it is impossible to select any one that would serve as an example to illustrate 
the problems involved in the rolling of the others. The accompanying 
prints show the shapes of the different passes for each of three types of 
rail joints, namely, the common splice bar, the Duquesne joint of the 
depending flange type, and the continuous joint of the bed plate type. The 
Braddock insulated joint is made up of two side plates and a bed plate, 
both being comparatively simple to roll. In a general way, rail joints are 
more or less difficult to roll, being subject to all the drawbacks of the rail 
section and to many others in addition, due to their irregular section and 
lack of symmetry. In the common splice bar, for example, the angles at 
which the section is rolled are limited by danger of undercuts, and the 
shape of the passes in which the piece is necessarily reduced are favorable 
to the formation of laps and seams. In the Duquesne joint, these dangers 






































RAIL JOINTS 


455 



Fig. 83. Passes for Rolling Common Splice Bar. 

























( 


456 THE ROLLING OF SECTIONS 



Fig. 84. 


Passes for Rolling Duquesne Splice Bar. 























RAIL JOINTS 


457 



Fig. 85. Eight Sections 130-31 Continuous Splice Bar. 
Sections on Pitch Line. 




























458 


THE ROLLING OF SECTIONS 


are multiplied, while the outstanding parts of the continuous section, by 
striking the rolls first or being a trifle colder than the rest, often prevent 
the piece from entering the pass rightly. For similar reasons, it is difficult 
to make guides that will properly handle this material, and it is prone to 
become cobbled or caught in the rolls of the tables. The base plate 
part of the continuous joint must be rolled at the angle as shown on the 
drawings. This part is later bent up hot at the splice bar shop to fit neatly 
the flange of the rail. After being rolled, usually in pieces about ninety- 
three feet long, the bars are hot sawed into three equal lengths, and sent 
to the splice bar shop, which is located at the Edgar Thomson Works. 
Here they are sheared to lengths required, punched, slotted and straightened 
by methods shortly to be described. 

Methods of Finishing Rail Joints: While the finishing of rail joints 
bears no relation to the rolling of them and is a separate industry, yet for 
the convenience of the reader it is best to complete the subject now, rather 
than to postpone it for some other part of the book. There are four ways 
by which rail joints may be worked: First, all the operations of shearing 
to length, straightening, punching and notching may be performed upon 
the cold pieces without heating in any way, when they are spoken of as 
cold worked joints. Second, this cold working may be followed by an 
annealing process to produce the cold worked and annealed bars. Third, 
the bars may be heated, after shearing to length, and the work of punching, 
etc., be done while they are hot, after which they are allowed to cool in 
air. In this case they are called hot worked bars. Fourth, instead of 
cooling the bars in the air after hot working they may be cooled by immers¬ 
ing them in oil, when they are designated as hot worked and oil quenched 
bars. It will be observed that all bars, no matter by what method they 
are to be worked, are sheared cold, hot or cold sawing being too expensive 
to be considered. Of course, these methods of treatment may be varied 
somewhat, but it is doubtful if the additional benefits derived are com¬ 
mensurate with the additional expense involved. 

The Edgar Thomson Splice Bar Shop: The practice at this shop 
coincides with that outlined above. For this reason the shop is made 
up of four units designated as A, B, C, and D, of which all may be used for cold 
working, but only A, B, and C are equipped with furnaces for hot working. 
The furnace of unit B is used for heating continuous joints prior to bending the 
depending flange. Units A and D each consist of a shear and two presses 
for punching. A gag press for straightening such bars as need it is also 
provided. Unit B, which is especially equipped for working continuous 
joints, consists, in addition to the furnace noted above, of one shear, two 
punches, and a folding press, which not only folds the joint but also 
straightens down the flange forming the bed plate, all in the one operation. 
The Duquesne bar likewise requires a special tool for cutting out the excess 
in the depending flange. For this reason, unit C consists of two punches, 
a straightening press, and two shears. A continuous oil quenching tank 




FINISHING RAIL JOINTS 


459 


and two large annealing furnaces complete the main equipment of the shop 
proper, while, in addition, a section of the shop is given to assembling 
insulated joints. A machine shop for making the dies for punching and 
shearing is housed in a building adjoining the working shop. 

Cold Worked Bars: In this method the order of working is this: First, 
the bars are sheared to length, inspected for straightness and flaws, 
straightened, if necessary, punched and slotted. The dies on the shears 
are, in all cases, made to conform exactly to the shape of the bars, so that 
a nice clean cut is made without in any way deforming the bar. However, 
in shearing the continuous joint, a slight bending of the outer edge at one 
end is unavoidable. For a similar reason, the bottom blocks, or dies, of the 
punching and notching machine support the web while the punches descend 
from above, pushing the material through conforming openings in the 
blocks. All dies are made of the highest grade of special tool steels and 
are kept in the best possible condition. In this way the hole is made as 
smooth as it is possible to make it by punching. It is evident that it is a 
great advantage to the shop to have the bolt holes on each bar alternately 
round and oval rather than all oval or all round, for in the latter case only 
every other bar could be punched on one arrangement of the dies, and the 
bars would require careful matching. As to the effect of cold working, it 
is quite clear that the bars of low carbon content, under .28% carbon, soon 
recover from the effects of the working, but in the higher carbon bars these 
effects are permanent and may do injury to the bar. On the entering side 
of the punches the metal is compressed beyond its ultimate strength, while 
the material on the opposite side is put under a tension, as may be observed 
by an examination of any hole made by punching. One of the direct results 
of this cold working is to increase the hardness of the metal about the hole, 
but the worse effect, which applies only to high carbon bars, is found in 
the very small cracks which extend into the metal along lines perpendicular 
to the surface of the hole. For these reasons, cold working is the most 
objectionable of all the methods cited. The difficulties, as well as the evil 
effects of cold working, increase as the carbon content of the steel increases. 
Hence, only low carbon bars (below .28% C.) should be cold worked. As 
a rule the method is applied to the smaller angle bars and fish plates. 

Cold Worked and Annealed Bars: The fine cracks due to cold working 
cannot be eradicated by subsequent treatment, but the internal stresses 
and strains are relieved by annealing and the bar as a whole is made more 
ductile. Hence, some specifications, more particularly on angle bars and 
insulated joints, will call for cold working to be followed by annealing. 
The annealing furnaces provided at this shop are divided into two sections, 
a heating chamber, which is fired with natural gas, and a cooling chamber. 
The bars to be annealed are piled, crib fashion, upon steel supports that 
rest on brick bottomed cars, which are pushed into the furnace. The 
furnace is then heated to a temperature slightly above the critical point of 




460 


THE ROLLING OF SECTIONS 


the steel. The proper temperature once reached, it is maintained until all 
the steel is thoroughly heated, which generally takes about two and one- 
half hours. The heat is then turned off and all doors in the furnace are 
closed. The steel is now pushed into the cooling chamber, where it is 
allowed to cool slowly. During this time the doors are closed tightly to 
prevent, as much as possible, scale forming on the steel. The cooling 
requires about two and one-half hours. After the steel is cold, the cars 
are pushed out of the furnace, and the bars are loaded on cars for shipment. 

Hot Worked Bars: In hot working common angle bars, the order of 
procedure is as follows: shearing to length, heating, punching, notching, 
straightening, if necessary, and cooling. Patented bars may require 
additional operations. Thus, in working the Duquesne bar, the excess 
flange is sheared off after the heating and just before the notching. In 
hot punching any bar, in order to avoid spreading of the metal and con¬ 
sequent distortion of the bar, it is necessary to employ a confining die, 
that is, the cutting die must be enclosed in a die block or frame, the upper 
surface of which, together with the die itself, conforms in shape to the 
inside surface of the bar. Hot worked bars must, therefore, be punched 
from the outside, or inward. Most cold worked bars may be punched from 
the inside, or outward, as there is no danger of spreading the metal and 
enclosed dies are not necessary. The straightening machines are presses 
provided with a set of dies for each size of each section. One die conforms 
to the size and shape of one side of the section and the second die to the other 
side, and both are set in the press so that at the end of the stroke the space 
between the dies is of the same shape as the bar and just equal to it in 
thickness. As a rule the higher carbon angle bars, Duquesne and con¬ 
tinuous joints are hot worked. In case the continuous joints are cold 
worked, they must be heated before the flange is bent down. The furnaces 
employed for hot working are of the continuous type. They are rectangular 
in shape and wide enough to admit two rows of bars laid end to end. Natural 
gas is the fuel used. In order to obtain an even distribution of the heat, 
the furnace is provided with four ports, and in addition four large burners 
of the Bunsen type are located at the bottom along each side of the furnace 
to supply heat under the bars. Recording pyrometers are employed, so the 
exact temperature of the furnace may be ascertained at any time. After 
being sheared to length, the cold bars are laid upon water cooled skid pipes 
and pushed into the furnace from the rear by means of electricallj’- operated 
dogs. The length of the furnace and rate of charging is such that about 
two hours are consumed in pushing each bar through the furnace, this 
time being sufficient to bring the bar to the working temperature of about 
800° to 830° C., which is a little higher than necessary for working, as the 
temperature drops by the time the bar reaches the machine to 790° or 815°. 
The skids end near the front of the furnace, and the bars descend to a hearth, 
whence they are removed with tongs through doors. Needless to say, the 
bad effects of cold working are entirely avoided by hot working. 





STRUCTURAL SHAPES 


461 


Hot Worked and Oil Quenched: In this method, not only are the 
evils of cold working avoided, but the strength and ductility, or toughness, 
of the bar are much improved, also. The method, which is especially 
applicable to high carbon angle bars and Duquesne joints, consists in hot 
working the bars in the usual way and quenching them in oil before they 
have cooled to a temperature below that of the critical range. The neces¬ 
sity of completing the work before the temperature drops below this point 
may require the bar to be heated to 30° or 40° C. higher than for ordinary 
hot working, and permits no delay in the operation. For quenching the 
bars, a continuous oil tank in close proximity to the presses is provided. 
The tank is rectangular in shape and provided with a chain conveyor, which 
slowly carries the bars through the oil, the speed of the chain and its 
direction of travel being so regulated that the bars, upon entering at one 
end of the tank, are carried down into the oil, across the tank, and up to 
the opposite end and are cooled to 70° C. or less. The oil used is a special 
grade of petroleum product that will not get viscous and has the most 
favorable cooling properties. In order to keep it cooled to the proper 
temperature, the oil from the quenching tank is pumped through a set of 
water cooled pipes and into a large storage tank. The fresh oil for the 
quenching tank is pumped from the bottom of this tank. By means of 
this circulating system the temperature of the oil is kept, usually, at about 
60° C. The temperature of the oil is taken at intervals of an hour or so 
to make sure its temperature does not rise too high. 


SECTION III. 

STRUCTURAL AND OTHER SHAPES. 

Plan of Stuay: It is needless to remark that a detailed description 
of the rolling of each of the many sections included under this heading 
would result in a very lengthy discussion; and it is doubtful if such a dis¬ 
cussion would prove to be of much value in accomplishing the ends at which 
this book aims. Besides, while the rolling of each shape or section presents 
difficulties peculiar to itself alone, there are certain problems common to 
all sections, and of these general features an example has already been 
given in the description of the rolling of rails. Unlike rail mills, structural 
shape mills vary much, both in type and equipment, and often the methods 
for rolling a given section must be adapted to the mill conditions. In 
general, the size of the section, for economic reasons, will determine the 
size of the mill, and the different sizes of the same section will be rolled 
on different mills. No one mill, therefore, can be selected as an example 
of the rolling of even one of these shapes. For these reasons a brief and 
more or less general discussion of the different roll designs for some of the 
more common sections is all that will be attempted here, and it is hoped 
the study will be found both interesting and profitable. 



462 


THE ROLLING OF SECTIONS 


Angles: Among the first shapes to be rolled was the angle. Three 
methods of rolling this shape have been developed. In two of these methods 
the forming of the angle is begun from a rectangular bloom, or if the bloom 
is square, from a rectangular roughing pass in the mill. In what may be 
termed the first method, the grooves are so designed that each successive 
pass from the slab approaches the right angle of the finished bar, the piece 
being gradually bent and reduced at the same time. In the second method, 
called the butterfly method, the legs are kept flat until the leader and 
finishing passes, when they are bent to form a right angle. In the third 
method, the forming of the angle is begun from a rectangular bloom by 
first working off one corner and then recessing it till the desired thickness 
of the legs is obtained. 



Fig. 86. Methods of Rolling Angles. 


The Three Methods Compared: The part of the angle that gives 
the most trouble in rolling is the back and the apex, which must be square 
and sharp. As shown in the accompanying sketches, this difficulty is 
overcome in the first and second methods by reserving metal in the first 
passes on both sides of the bar where the apex is to be formed. In the 
last passes this excess metal is available to fill out what would be lacking 
on account of the bending, which tends to draw the metal down from the 
apex. In the third method the apex and back are perfect from the beginning. 
As to the relative merits of the three methods, there is, of course, much 
difference of opinion. However, there are two features about the butterfly 
method that appears to a decided advantage when compared with either 
of the other two. The ability to employ an edging pass so near the finishing 






























































STRUCTURAL SHAPES 


463 


to control the width makes it possible to reduce the piece rapidly in the 
roughing passes and so cut down the total number of passes required to 
form the section. Then, too, since nearly all the work on the section is 
done in the flat passes, the difficulties encountered when deep grooves are 
used in the rolls are entirely avoided. Usually angles are formed in from 
nine to eleven passes. 




Butterfly Method for Channels as first designed 




Fig. 87. Methods of Rolling Channels. 

































































































464 


THE ROLLING OF SECTIONS 


The Channel: Channels are rolled by two distinct methods known 
as the butterfly and beam roughing methods. The butterfly method is 
said to have originated in the year 1873 at the Upper Union Mills of Carnegie, 
Kloman & Co., and is sometimes called the slabbing method. In being 
formed by this method, the section resembles two angles being rolled side 
by side in one set of grooves, and by the same butterfly method. In the 
second method the bloom, in the rectangular form, is edged for the first 
pass and is then worked down from each edge or face alternately by grooves 
in the roughing passes until it much resembles a beam, and in reality it is 
a beam in the rough. Succeeding passes, however, work off the flanges on 
one side of the web. The function of these temporary flanges is to supply 
metal for holding the height of the flanges on the opposite side, thus forming 
a channel with full sharp edges and square sides. This method is said to 
have an advantage over the butterfly method in that the roughing rolls 
may be used either for beams or channels and a greater number of weights 
may be taken from the same set of rolls. In rolling deep channels the 
butterfly method would appear to overcome the difficulty of making the 
flanges nicely, but more roll space is required than in the beam roughing 
method, and since the great width of the section makes edging imprac¬ 
ticable, it is more difficult lo secure well formed edges on large channels. 
In the beam method, the butterfly idea is used to some extent, and in order 
to obtain the proper height and thickness of flange readily, the flanges are 
rolled at an angle to the web and finally bent to right angles in the leader 
and finishing pass in the same way, though to less degree, as in the butter¬ 
fly method. For channels, about the same number of passes are required 
as for angles. Very large channels are often rolled from shaped blooms, 
as at the thirty-five inch mill at Homestead, which works in conjunction 
with the forty inch blooming mill to roll large beams and channels. The 
blooms for both these shapes have much the same form, the channels being 
finished by the beam-rougher method in the thirty-five inch mill. 

Beams, Ties, and Piling: Beams were, doubtless, first made by 
riveting a plate and four angle bars together, then later by bolting or 
riveting two channels together back to back. Up until 1895 they were 
considered very difficult sections to roll, but the great demand for these 
shapes during the succeeding j^ears so stimulated thought in their manu¬ 
facture that most of the former difficulties have been overcome, and standard 
beams are now rolled with as little trouble as angles, channels, or rails. 
Indeed, the rolling of these sections very much resembles that of rails, 
for if the head of the rail be replaced by a flange the sections would be 
practically the same. Like rails, there are two methods of rolling beams, 
namely, the flat, or slab-and-edging, method and the diagonal. But un¬ 
like rails, the diagonal method for beams is far superior to the older flat 
method, because the oblique design of the passes makes it possible to secure a 
much greater length of flange than was ever produced by the first method. 
This advantage is forcibly illustrated in the steel tie section, the rolling of 




STRUCTURAL SHAPES 


465 


which was first successfully accomplished at Homestead. This section with 
its very thin flange, which has almost no taper, would have been looked upon, 



Fig. 88. Methods of Rolling Beams. 









Ilk 

w 

rrr 

1 


u 

>-A 



Fig. 89. Methods of Rolling Piling. 


fifteen years ago as an.impossibility from a rolling standpoint, and is con¬ 
sidered one of the greatest achievements in roll design. TJ. fe. steel piling 






















































































































































































































































































466 


THE ROLLING OF SECTIONS 


is another section which much resembles the rail in rolling. Here, the ball 
and web of the piling, as finished, is almost a duplicate of the head and web 
of the rail, and the remainder is rolled as a flange up to the leading and 
finishing passes, when the two halves or legs are bent down to form the 
socket for the interlock. It is rolled either by the flat or diagonal methods. 

Zees and Tees: Zees may be looked upon as double angles or channels 
with reversed legs, or flanges, and the methods of rolling correspond to the 
first two methods for angles. As to tees, it is doubtful if any other section 
offers as little opportunity for variation. There is only one way by which 
the tee can be rolled. In this method the shaping begins from a square bil¬ 
let or bloom. One side of the square is retained to form the base, or table, 
of the tee, while the edges of the opposite side are both recessed in the 
first forming pass by collars on each side of a groove into which part of 
the metal flows to start the stem. The piece is then edged for the next 
pass, in which the stem is reduced between the flat surfaces of the rolls, 
while the two parts of the table pass through grooves in the two rolls. 
In the next pass the piece is turned with the stem up, which will pass 
through an idle groove, while the table on each side of the stem will be 
reduced between the plain surfaces of the. rolls. This process is then 
repeated, the piece being worked alternately on the stem and table, until 
the section reai hes the size desired in the finishing pass. Usually, in this 
last pass the stem is in the groove of the lower roll and the table is 
reduced between the rolls. In order to prevent the bar from following the 
roll on the delivery side, this groove, as for all the idle grooves, must taper 
slightly from the top and be large enough to give easy passage for the stem, 
thus making it somewhat wider than the stem is thick. The reduction of 
the table then results in the formation of a slight overfill at the base of the 
stem. This bit of excess metal cannot be removed, because the stem was 
necessarily finished in the preceding, or leading, pass. If the section were 
finished by working on the stem, the same defect would be developed. 

Finishing Sections: Most shape mills are provided with hot saws 
located after the finishing pass and near the cooling beds. These saws are 
intended mainly for cutting test pieces, but in some mills they are used 
for cutting off crop ends or dividing mill lengths where the cooling beds 
are too short to take full mill lengths. The test pieces are of two kinds, 
namely, those for the roller, whose duty it is to see that the section is rolled 
to the correct dimensions and weight, and those for the physical laboratories. 
With these exceptions, however, the full mill length is sent directly to the 
cooling bed. Here, as in the case of rails, the cooling causes the shapes 
to bend considerably, and cold straightening is necessary. For this purpose, 
the piece is next passed through a cold roll straightening machine, and if 
necessary through a gag press. The roll straightener is capable of 
straightening in one direction only, so that if, through handling or other 
cause, the piece has been twisted or bent laterally, it can be made straight, 




ROUNDS 


467 


in all directions, only by using a gag press after the roll straightener. From 
the straighteners the material passes the cutting machines, which, in order 
to keep up with the mill, must be either shears or cold saws. For this 
reason, exact cutting to length is out of the question, and a liberal cutting 
tolerance is always desired by the mill. As a rule, angles, zees and small 
tees are sheared, while channels, beams and large tees are cut with cold 
saws. During the cutting, any material that contains the more noticeable 
defects is discarded and cut into scrap lengths, and after the cutting the 
material is subjected to a very rigid inspection for the most minute surface 
defects. 

Rounds: In the steel business, rounds are often designated as hand 
rounds or guide rounds, and these terms are indicative of the two methods 
for rolling these shapes. In the first method, the bloom or billet is first 
reduced in diamond shaped roughing passes to the form of a round cornered 
square. Then, by means of tongs in the hands of the workmen, this square 
is supported in the correct positions and passed through a single round¬ 
forming, oval-shaped pass, or two similar round-forming passes, until it has 
been worked into the round form, which can be accomplished by turning 


Billet 



Y* Rounds 

Fig. 90. Rolling a Half Inch Guide Round. 


the piece through an angle of 90° after each pass through the rolls. From 
three to five passes in the finishing stand are required to form the round 
by this method of rolling. In the case of guide rounds the size of the billet 
may be reduced in the roughing passes in a manner similar to that for hand 
rounds, or by any other method that will give a round cornered square. 
This square is then reduced in one or two passes to an oval, which is then 
edged, and while supported in this position by a guide, it is put through 
a round finishing pass. The compression in this pass shortens the long 
axis, while the spreading of the metal lengthens the short axis of the oval 
to equal the radii of the round. In a general way, large rounds, that is, 
those over two inches in diameter, are rolled by hand, while small rounds, 







468 


THE ROLLING OF SECTIONS 


less than two inches in diameter, are rolled with guides, but there is a 
narrow range from about one and three-fourths inches to two and one-half 
inches where either method may be employed. Regarding the relative 
merits of these two methods, hand rounds are by many preferred to guide 
rounds where great accuracy and uniformity in diameter are required. 
However, guide rounds are now rolled with a high degree of accuracy, and 
since the uniformity and accuracy of the hand rounds depends on the skill 
of the workmen, it is doubtful whether equal care and attention applied 
to both methods would leave, on the average, much wherewith to choose 
between them. 

Cutting and Straightening Rounds: In order to keep up with the 

mills, rounds are either hot sawed or cold sheared to convenient lengths, 
and neither method is at all exact. Hence, in these lengths, either single 
or multiples of those desired, proper allowance must be made for the exact 
cutting, which is performed by special cutting machines after the round is 
straightened. The straightening may be done either on the gag press or 
on special straightening machines, called from the inventors the Brightman 
and Abramsen straighteners. The Brightman consists of two rows, or sets, 
of concave rolls moimted upon opposite sides of a revolving frame, so that, 
with their axis of rotation at an angle to that of the frame, the concave 
surfaces of opposite rolls bear on the round and grip it in such a manner as 
to force the bar along longitudinally and at the same time bend it .at the 
crooked places enough to straighten it. In the other type of machine the 
rolls are mounted on a stationary frame, while the piece itself is revolved 
and forced through it. The straightening develops one serious defect, 
which renders the bar unsuitable for some purposes. The scale in the spiral 
path of the rolls is rolled into the surface, causing a slight pitting, which 
can be removed only by machining. 

Flats: Because they are the simplest, the flats w T ere the first sections 
to be rolled. The main problem involved in designing the rolls for flats is 
the control of the width, which is done in two ways after the piece has left 
the roughing rolls. The first method, called the flat and edging, consists 
merely of rolling the piece on edge at intervals in deep grooves cut in the 
rolls. The other method of controlling the width lies in the use of the 
tongue and groove passes as described under the rolling of sheet bars, and 
is best suited to the rolling of thin material. In this method the last two 
passes will be between plain rolls, while in the flat and edging method the 
planisher will be an edging pass. It is in this pass that the three different 
edges on flats are formed. Thus, if the bottom of the groove is flat, a 
common swell or oval edge will be formed by the spreading of the material 
in the center, which is hotter than the outside; but if the base of this groove 
is made sufficiently concave, the edge of the bar will be round; if convex, a 
square edge will be formed. In the eighteen inch mill at Clairton and also 
in the fifteen inch mill at Lower Union City Mills there is used, next to the 
finishing pass, a set of vertical rolls, which eliminates the difficulty of 
rolling a wide thin flat in an ordinary groove. 








HEXAGONS AND DEFORMED BARS 


469 


Hexagons: There are two methods used for rolling hexagons. By one 
method all six corners are formed in the rolls, three in the top and three in 
the bottom. The clearance between the rolls in this case comes on opposite 
flat surfaces of the bar. In this manner of rolling, the corners of the hexagon 
cannot pinch out. Hexagons rolled thus are best suited for cold drawing 
purposes as they will be free from pinches which draw out into laps. In this 
method, the first pass in the strand, or first former, is a square which has 
been broken down from the billet in the roughing and pony roughing stands. 
The square is then put into the second strand, or former, and comes out 
in the form of a six sided flat, the two widest sides of which are convex. 
The bar is then edged into the leading or planishing pass where a reduction 
of about 25% takes place, in the case of small hexagons. The bar coming 
out of this pass has six sides as before but has two of its corners formed 
by the clearance of the rolls. The top and bottom sides are slightly concave 
to allow for the spread as the bar is edged into the finishing. Here the 
bar is given a light draft, in order to square it up, the reduction being only 
8 to 10%.In the other method two of the corners of the finished bar are 
formed at the clearance of the rolls, and hence care must be taken to keep 
these corners from pinching out. The bar coming out of the planishing in 
this method, is in the same position as the finished bar of the first method. 
The bar is turned 90° and entered into the finishing so that its top and 
bottom surface are flat or horizontal and two of its corners are in the 
clearance between the rolls. In the one method but three passes are 
required to form the finished bar from the square while the other method 
requires four. 

Deformed Bars: This term is meant to include any bar having an 
irregular surface or a surface on which there are projections or depressions, 
such as the various concrete reinforcing bars, clip iron, hame strap, etc. 
Some of these bars are so complex as to excite the highest admiration and 
astonishment from those not familiar with their manufacture. While they 
require the greatest ingenuity on the part of the roll designer, they are, 
however, produced with less difficulty than might be supposed. Briefly, 
the secret of their formation consists in first working the metal down through 
the ordinary passes to one of the common forms, such as a flat, square, 
round, or oval, whichever is best for forming the bar desired, and then 
putting it through one or two deforming grooves containing the necessary 
recesses or elevations. It is here the chief trouble occurs. As the deforma¬ 
tions must be made in the finishing pass, or the leader and finishing com¬ 
bined, a heavy draught in these passes is necessary, and the metal is usually, 
even with the fastest working, at a very low temperature for working, 
These conditions put a heavy strain on the mill, and, owing to the lack 
of plasticity in the metal, the projections will not fill out easily. In order 
to avoid vibrations which cause the bar to slip in passing through the rolls, 
thus causing the deformations to be made at irregular intervals, mills 
rolling these sections are provided with separately driven finishing stands 





470 


THE ROLLING OF STEEL 


CHAPTER IX. 

THE ROLLING OF STRIP AND MERCHANT MILL PRODUCTS 

SECTION I. 

STRIP, OR HOOP, MILLS AND THEIR PRODUCTS. 

Meaning of the Word Hoop: As originally applied, the word hoop 
meant that light narrow material which, cut into short lengths, was used 
to bind casks, barrels, buckets, and the like, but as now employed the 
word is a class name that stands for a large number of products. The 
Carnegie Steel Company, for instance, uses the term to cover all materials 
from 13 gauge to the thinnest material rolled on their mills, and from three- 
eighths inch to eight and five-eighths inches in width. This range covers 
material used for a great variety of purposes in addition to hoop, such as 
skelp for tubes, blades for knives, and blanks for stamping hundreds of 
hardware specialties, a class of material that should represent a little better 
grade than ordinary hoop. In a way, this use of the word hoop is unfortu¬ 
nate, especially as a more suitable class name is supplied by the term strip. 
With strip for a class name, hoop would have retained its original meaning, 
for which there is no substitute, and all danger of ambiguity would have 
been avoided. 

Hoop as a Rolling Specialty: Being, perhaps, the largest pro¬ 
ducer of strip in the country, the Carnegie Steel Company’s mills furnish 
the best example of the equipment and organization required to roll this 
class of material. A specialty mill is not a mill that rolls a specialty 
nor a variety of specialties, but one that has specialized in the rolling of 
a single product. According to this definition, and using the term hoop 
in its broad sense as outlined in the preceding paragraph, the hoop mills 
of this company are best described as specialized specialty mills, because 
they are laid down, not for the general purpose of rolling hoop or strip, but 
in such a manner that each mill is designed and equipped to roll a certain 
kind or grade of hoop. The advantage of such a system is at once evident, 
making it possible for the mills to meet the many demands of the trade 
most readily. Thus, they are able to give accuracy, where accuracy is 
required; finish, where finish is desired; quantity, where quantity is the 
main consideration; and all with a better quality to the customer and at 
a greater saving to the producer than would be possible in any other way. 

The Carnegie Hoop Mills: From what has just been said, it will 
readily be surmised that the hoop mills of this company are many in number 
and of various types, and no detailed description of all of them can be 



HOT STRIP OR HOOP 


471 


expected. This excuse will be better appreciated when it is known that 
their hoop mills number no less than twenty-five, and among these at least 
six types, or designs, of mill are represented. However, these mills present 
certain features of a general nature, for the omission of which no valid 
excuse can be found. In size their hoop mills range from seven to twelve 
inches, the most common size being eight and ten inches. In some of the 
mills the different stands of rolls will vary in size. Thus in the McCutcheon 
No. 6 Mill, eleven inch rolls are employed in the roughing stands, nine 
inch in the intermediates, and eight inch in the planisher and finisher. 
The rolls may be of different sizes in the same stand, also, as will be explained 
later. As to the materials of which the rolls are made, the roughing rolls 
may be of steel and the intermediates of sand or adamite, but the finishing 
rolls are always of the hardest chilled iron. The number of stands in these 
mills vary from eight to twelve per mill, and their arrangement is such as 
to produce the kind of hoop desired to best advantage, as will be more 
clearly explained later. 

Methods of Rolling Hoop: While hoop of the heavier and medium gauges 
and narrower widths is successfully rolled by the flat and edging method, 
it is readily understood that this method is not applicable to all sizes of 
hoop. After the material leaves the roughing rolls there is but one way 
remaining, then, by which it can be reduced, and that is by the tongue and 
groove method already described. These tongue and groove passes will be 
found to be three or four in number, though only two are used in some of 
the mills, and to be followed by two or three stands of plain rolls. As to 
the manner of breaking down in the roughing stands, there are two methods 
of rolling—one in which the billet is reduced by flat and edging passes and 
another in which the roughing passes are ovals and squares. The latter 
method gives a more rapid reduction, and will be employed usually where 
only two roughing stands precede the tongue and groove rolls. 

Precautions Required in Rolling Hoop: The chief difficulty 
encountered in rolling this light strip lies in getting the hoop through the 
rolls before it becomes too cold to roll, or in keeping the temperature 
uniform at the finishing roll, which is necessary to produce a strip uniform 
in gauge. Considering the rapidity with which the metal is cooled on 
account of the thin section and the chilling effect of the cold rolls, the 
accuracy as to gauge and width maintained by the hoop mills is little 
short of astonishing. In this case the ingenuity of the engineer who builds 
the mill and that of the roll turner who designs the rolls are both required, 
in addition to the skill of the rollers, to produce the desired result. By 
reducing the number of passes to a minimum in the ways already described, 
the roll designer has done his bit, but even then the last end of a long strip 
will be cooled to a temperature so much lower than the first that it will 
finish several thousandths of an inch thicker, unless the mill is adapted to 
rolling it. These drawbacks are overcome by a combination of ingenious 





472 


THE ROLLING OF STEEL 


schemes. First, the mill is run at as high a speed as practicable. Second, 
it is arranged and operated so that as little time as possible intervenes 
between passes. Thus, in the more modern hoop mills, roughing rolls on 
the continuous plan are used, and these are placed very close to the furnace, 
whence the billet, being at once reduced in the two or three roughing passes, 
passes over roll tables to the tongue and groove rolls, which are arranged 
on the continuous plan or in train. If the latter plan is followed, mechanical 
repeaters are employed for short lengths, or the piece is looped from pass 
to pass by hand, by which means it may be rolling in two or more stands 
at one time. In order to avoid having the loop, which increases with the 
length of the piece, run far out on the floor, and thus become chilled, each 
pass following the tongue and groove passes is made to run as much faster 
as its predecessor as is necessary to take up the slack due to the elongation. 
Other schemes to equalize the finishing temperature are also employed. 
It is said that at some hoop mills the end of the billet which represents 
the last end of the hoop to pass through the rolls is heated to a 
higher temperature than the first end. In the cotton tie mill at Youngs¬ 
town, where the strips are about 1800 feet in length, one end of the billet 
will be in the furnace, while the other will be coiling some 200 feet away 
at the other end of the mill as finished strip. Other factors affecting the 
uniformity of gauge, or thickness, are the wear of the rolls and the bearings. 
To overcome the wear of the former, which also affects the finish, the 
path of the piece through the leading and finishing passes is moved over 
to a new surface about every twenty minutes, or whenever these surfaces 
become too rough. The vibration of the mill pinions produces waves or 
slip marks on the surface, if the last stands are in train with the tongue 
and groove rolls, hence the planishing and finishing rolls are generally 
separately driven in mills rolling the best grades of hoop, and only one 
of the rolls is driven, the other revolving by friction due to contact 
with the driven roll. The planisher may be in train with the tongue and 
groove rolls, but the finishing stand is almost always separately driven. 
At some of the mills where the finisher or planisher, or both, is in train 
with the rest of the stands, the bottom roll is much larger in diameter 
than the top roll or the rest of the mill, and is driven, while the top roll 
revolves by friction. The larger diameter of the bottom roll increases the 
speed of delivery of the stand. The finish on some hoop is of great im¬ 
portance. To provide for this requirement scrapers are employed in front 
of the chill, or finishing, rolls. These scrapers consist of two horizontal 
bars spaced about eight inches apart and fixed parallel to and just in front 
of the rolls, and of two other bars similarly arranged but fastened to the 
two prongs of a fork that can be moved up and down by means of a lever. 
In this way the movable bars can be lowered as desired into the spaces 
between the fixed bars and the rolls. As soon as the rolls grip the piece 
the scraper is brought into action, and the piece is bent sharply up and 
down over its edges, thus cracking the scale and removing it at once. As 





HOT STRIP OR HOOP 


473 


the piece, after coming out of the finishing pass, is near or below the critical 
temperature, no more scale is formed, and a smooth bluish surface results. 
About five or six feet of hoop on the front end is not thus scraped, because 
the great speed of the piece carries it through this distance before the 
scraper can be brought into play. In order to eliminate this unfinished 
end with as little waste as possible the shears are located, preferably, at 
the mill end of the cooling bed, so that this end of the strip is the last 
to be cut. The adjustment of the rolls is also an important matter in 
rolling hoop. To illustrate this point, if one of the finishing rolls is enough 
out of level to make a difference of only one-ten-thousandth of an inch in 
the thickness of the hoop on its edges, it will bend toward the heavy side 
in leaving the pass an amount equal to one foot in thirty feet of length. 
As the stiffness of an ordinary hoop is only sufficient to push it, even on a 
very smooth run out, a distance of about thirty feet, some means of cheaply 
delivering the strip away from the last stand of rolls must be used. In 
Carnegie mills, this delivery is accomplished in three ways, namely, by 
hot coders, by conveyor belts in the runouts, or by pneumatic runouts. 
In the last named type of conveyor, air blown at high pressure through 
holes in the bottom of the runout and at angles directed away from the 
mill, lifts the strip, decreases the friction and helps to carry it along. 

Finishing Hoop: Hoop may be finished in many ways. As to the 
cutting of hoop, it is always cold sheared, and this may be done so as to 
give either both ends square or one end square and one end round. x’For 
this kind of cutting, a special die with a double edge, one round, the other 
square, is used, and the shapes on the ends of the hoop are formed by 
punching out a small part of the hoop. Ordinary hoop, not coiled, is cut 
on alligator or small guillotine shears, but the cotton tie mill is equipped 
with two shears of a special type, which consists of two revolving wheels 
on each of which a shear knife is mounted. By regulating the relative 
speeds of the wheels, these shear-blades are brought together in every so 
many revolutions, so that as the strip is fed into the shear at a definite 
speed, it is cut into approximately equal lengths. Anything near exact 
cutting is impossible on this machine, due to slipping of the belts and the 
play in the parts of the machine. Flaring and punching machines are 
provided at some of the mills, and in this connection it is to be remembered 
that the flare on a hoop is measured correctly by one-half the difference 
between the largest and smallest diameters. All three methods of bundling, 
in strips, in scrolls and in coils, are practiced. As to coils, some of the mills 
can coil in multiple or single strips, while others can coil only in singles. 
Hot coiling can be done only at certain mills, also. It is a matter of pride 
with the men at the mills to turn out the finest product, and any order 
that calls for extra quality and finish is sure to receive the attention it 
deserves. On such material special tests, such as the acid test for scale 
pits and bending-over tests for seams, are often made in addition to the 
ordinary inspection for surface defects and gauging for thickness and width. 




474 


THE ROLLING OF STEEL 


SECTION II. 

MERCHANT MILLS. 

What the Merchant Mill Is: The first mills were what we of to-day 
would call merchant mills, though the term was perhaps not then applied 
to them. In the beginning of the industry, all mills doubtless rolled a 
variety of simple sections such as rounds, squares, flats, etc., but as the 
business grew and the demand for heavier material and for certain shapes 
increased, mills designed to meet a given demand or to roll a certain kind 
of product began to appear. Then it was that the smaller or older mills, 
which continued to roll a variety of sections and often stocked material 
that was retailed out later, were designated as merchant mills, in order to 
distinguish them from the specialty mills and those whose product was 
handled in large lots. Later on, especially in this country, the mill manner 
of handling materials and doing business underwent a change, and the mills 
were more or less divorced from the store house, so that these mills, while 
they continue to roll a variety of sections, always roll to orders. Thus, 
though they have lost all the characteristics, they still retain the name of 
merchant mills. Therefore, in this country a merchant mill is any small 
mill, say twenty-two inches and under, which regularly produces more than 
one shape. 


Kinds of Merchant Mills: In touring the various works, the visitor 
is surprised and often not a little confused by the great number of and 
seemingly meaningless terms applied to these mills. Thus, there is heard 

the term “bar mill” applied to two 
mills of altogether different types. 
The term “guide mill” is apparently 
used in the same way. Added to 
these are such names as “Morgan 
mill,” loop mill, shape mill, con¬ 
tinuous mill, and semi-continuous 
mill, hoop mill, Belgian mill, com¬ 
bination mill, etc., and such local 
terms as the “iron mill,” and the 
“steel mill,” the “electric mill,” 
or just “merchant mill,” as at one 
of our own plants where there is 
but one merchant mill. While one 
not familiar with the mills is inclined to think most of these names are 



Fig. 91. 


Elevation 

First Merchant Rolling Mill. 


accidental localisms, many of them are really descriptive of the mills and 
also form links in a systematic classification based mainly on construction 
and design. These terms and the classification of the mills is best 
explained from a historical viewpoint. For this reason it is desirable to 
trace very briefly the evolution of the small mill. 



























MERCHANT MILLS 


475 


Development of Merchant Mills: The first mill, which also stands 
for the simplest kind of mill, consisted of a single stand of rolls driven in 
one direction only, and for many years all bars or sections were rolled on 
this simple mill. No guides were used at first, and the roller guided and 

supported the bar between the rolls 
by means of tongs. In order to 
avoid the labor of pulling the bar 
around the mill, the catcher re¬ 
turned it by laying one end on the 
top roll, which carried the piece 
forward with little effort on the 
catcher’s part. To avoid this idle 
pass, the idea of placing a third 
roll above the second, so as to 
work the bar as it passed in both 
directions, was conceived and re¬ 
sulted in a great economy in labor. 
Up to this point the bars were com¬ 
paratively short, sixteen to twenty 
feet being the usual lengths. It 
was next discovered that a great 
saving in both labor and material 
could be effected by making the 
bars longer, but to accomplish this 
increase, a larger billet had to be 
used. The increase in the size of the billet was secured by increasing its 
length, which required wide heating furnaces, and by increasing the size of 
its cross section, which called for a greater number of passes for reducing 
than could be placed in one stand. To supply these extra passes, addi¬ 
tional roll stands were needed. These stands were coupled together to 
form the roll train of Figure 92. 

The Guide Mill: The rolling of rounds, which have always been an 
important product, led to the first use of guides. The method first used 
was like the method for hand rounds previously referred to, but a greater 
number of passes were used to finish the piece. Since the tonnage, 
especially on small rounds, was held down by the time consumed in passing 
the piece back and forth through the finishing groove, it was natural that 
the mill man should seek some way of reducing the number of these passes. 
This endeavor led to a really great discovery, namely, that a round could be 
rolled in one pass from an oval, provided the oval was of the right dimensions 
and was supported by metal guides. This success of the guide led to its 
use for other shapes, also, and to its adoption in modified forms to nearly 
all mills. Thus, another word, guide, came to be rather loosely used. In 
general, a guide is any device used to support the piece in the correct 
position during its passage through the groove. In order to perform this 




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Elevation. 



Fig. 92. Diagram of a Simple Tjpe of 
Three-High Merchant Mill. 





















476 


THE ROLLING OF STEEL 


function, the guide must fit neatly against the roll or rolls, so one end must 
be shaped to conform to the shape of the space in front of the rolls. 
Entering guides are usually of the closed type, hhey are made in two parts. 



In each of these two parts a groove is cut parallel to its long axis, so that 
when the two parts are fitted together the opening formed by the grooves 







































MERCHANT MILLS 


477 


will be of the required shape of section to support the piece properly. The 
guide proved to be of immense advantage in another way, in as much as it 
permitted the rolling of very long lengths. Today, any mill designed to 
roll sections that require the use of guides may be called a guide mill. 


The Belgian and Looping Mills: Though it was now possible to 
roll in long lengths, a serious drawback was encountered in the old and 
slow-going mill, for, if the piece were long and, especially, if the section 
were small, the steel would get too cold to roll before the piece could be 
finished. The remedy, of course, was found in greater speed, but here 
trouble was again encountered because of the roughing rolls which refuse 
to bite the billet if the speed is too great. Then there originated in Belgium 
the scheme of setting up an independent roughing stand that could be driven 

from the main drive shaft of the en¬ 
gine at a lower speed than the finish¬ 
ing train, which was driven by power 
transmitted by belt from a large 
pulley on the drive shaft to a much 
smaller one mounted on a short 
shaft connected with the train 
pinion. Up to this time the piece 
was rolled throughout its length 
in a given pass before it was 
started into the next. Who the 
man was, or what his degree, that 
was responsible for the next ad¬ 
vance in rolling, history does not 
say, but doubtless it was some 
Fig. 94. Early Type of Looping Mill. bold Belgian catcher who first con¬ 
ceived the idea of catching the first end as it came through the rolls and 
returning it immediately through the next pass, thus rolling the section in 
two passes at once. Since the speed of the piece on the delivery side is 
greater than that of the rolls, due to the elongation, the material overfed 
and formed a loop. By this looping scheme, the capacity of the finishing 
train was increased beyond that of the roughing stand. 





The Semi=continuous or Combination Mill: Such was the extent 
of the development until a few years prior to 1900, when two things com¬ 
bined to force another advance in the merchant mill; one was the previous 
development and success of the continuous mill as a semi-finishing mill; 
the other was the necessity for economy due to labor troubles and a severe 
depression in the steel business. So, in order to decrease labor costs and 
speed up the mill to the limit of the finishing train, the continuous rougher 
was installed to replace the single three-high roughing stand of the Belgian 
mill. By this inovation the mill force was decreased by about nine men, 
while the output was increased 50%. The mill proper was then in a position 






































478 


THE ROLLING OF STEEL 



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rH'~ l ~ r ‘ m m 

32 


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Fig. 95. General Layout for a Ten Inch Mill—Later Type of Looping Mill with Continuous Roughing Stands. 






































































MERCHANT MILLS 


479 


to roll in unlimited lengths and thus effect another saving; but two things 
combined to limit the length of the piece rolled, namely, the difficulty of 
handling long pieces on the old style cooling bed and the problem of keeping 
the bar uniformly hot for finishing. The first problem was solved by the 
invention of the mechanical cooling bed. These beds consist of a runout, 
in which are live rolls, for delivering the piece; a device for stopping and 
transferring the material, which is delivered at speeds as high as twenty- 
five feet per second, and at intervals of only one or two seconds between 
pieces; a system of notched or fingered racks, by means of which the hot bars 
are moved away from the runout; and a receiving table, also containing live 
rolls, by means of which the bars are delivered to the shears. Examples 
of these tables will be found at all modern mills. The problem of uniform 
heat was then solved by speeding up the mill; by locating the roughing 
rolls near a continuous furnace, as was pointed out in discussing the rolling 
of hoops; and by arranging the drive of the mill so that the peripheral 
speed of the rolls is increased in the successive passes to take up the slack 
in the loops. Another device, by which the number of hands employed 
about the mill was reduced, is the mechanical repeater. Many mills 
equipped with these repeaters are entirely automatic in operation of the 
rolls, and can roll material that is much too stiff to be turned or looped by 
hand. 

The Cross Country Mill: While these improvements were being made 
in the looping mill, a mill of a different type altogether has been developed. 
It is known as the cross-country mill, and is intended for rolling material 
that does not lend itself well, on account of size or shape, to loop mill rolling. 
These mills involve the continuous idea, but the stands are placed so far 
apart that the piece must leave one set of rolls before entering the next. 
For carrying the piece from stand to stand stationary roll tables are em¬ 
ployed. To save space and avoid complicating the drive the stands may 
be arranged on two or more parallel lines, and the direction of travel of 
the piece will be reversed during the rolling. Three-high stands are placed 
at the reversing points, so that, by means of mechanical repeaters and 
diagonally placed tables, the feeding of the mill is made automatic through¬ 
out. In the latest types of these mills, as for example the No. 7 mill at 
Duquesne, which made its first trial rolling in July, 1917, the three-high 
stands have been eliminated and two-high substituted, the piece being 
moved over from the first roll line to the second then to the third by transfer 
and skid tables. In general, the tendency is to return to the two-high 
stand, because it is the simplest as well as the strongest and most rigid 
in construction. 

Future Development: From the preceding sketch, it would appear 
that the merchant mill, so far as the mill is concerned, has been developed 
almost to the highest stage of perfection. At present, the trend of improve¬ 
ment is in two directions, one looking toward economy in power and the 



480 


THE ROLLING OF STEEL 



Heating Furnace Heating Furnace 


Fia. 96. General Layout for Eight Inch (top) and Ten Inch (bottom) Electrically Driven Merchant Mills. Examples of the 

most Recent Types showing part only of each Cooling Bed and Heating Furnace. 




















































































































































































































































































































































MERCHANT MILLS 


481 


poq 3uijooo ox 















































































































































































































































































































482 


THE ROLLING OF STEEL 


other toward specialization. As to the first, the adoption of electricity for 
driving the mills promises to effect economies. Much advancement has 
been made since 1900 in the construction of electrical motors, which, through 
supplemental equipment such as rotating resistors, balancing sets, etc., 
have reached a very high state of efficiency, and a great majority of the 
mills installed since 1916 are equipped with these motors. Specialization 
is taking two courses. Thus, more and more specialty mills are being 
erected, and other mills are being supplied with special equipment, such 
as supplementary roll stands, which adapts them to the rolling of certain 
sections yet leaves them free to roll other products, also. 


SECTION III. 

DESIGNING ROLLS AND MAKING UP SCHEDULES FOR MERCHANT MILLS. 

Roll Designing for Merchant Mills: It does not require much imagin¬ 
ation to see that the problems of the roll designer for merchant mills are 
many and the most difficult to solve. That the art of designing rolls for 
these small mills must have made wonderful progress is indicated by the 
recent appearance of sections of the most intricate design, yet rolled with 
minute accuracy. But the designing of passes for the sections is but one 
of the problems confronting the roll designer, as a visit to the mills will 
show. Among these should be mentioned the great number of designs, 
which require the most systematic filing and recording of rolls, templets, 
and tools. The ingenuity of the roll designer is taxed to the utmost to 
keep the number of rolls at a minimum. So, the visitor in the mills will 
find that numerous sizes, differing by only a few thousandths of an inch, 
are placed in the same roll. The efforts of the roll designer along this 
line are especially noticeable in the roughing stands. Here the process is 
merely one of reduction, the piece leaving the roughers in the form of a 
square or rectangle. To bring about this reduction one of five methods, 
or combination of passes, may be employed. Thus, in continuous roughing, 
the student will observe four methods in use, which may be designated as: 
1. Diamond—square; 2. Oval—square; 3. Flat-and-edging; 4. All- 
diamond-to-square. In three-high roughers, either the flat-and-edging or 
the diamond-pass method is used. The following sketch is intended to 
illustrate these methods. Nearly all the shaping, except in the case of 
deformed bars already alluded to, is done in the stands, called the strands, 
immediately following the rougher. The strands are sometimes preceded 
by an auxiliary set of roughers called the pony roughers. The planisher 
may be employed as a last forming pass only or, in addition, to give a finish 
to the bar. The finishing pass is reserved exclusively for removing the 
little irregularities of the previous rolling. 

Economic Features of Roll Designing: It scarcely needs to be 
pointed out that aside from the successful rolling of the various sections, 
the chief incentive behind the efforts of the merchant mill roll designer 




Continuous Roughing Three-High Roughing 

Diamond Square Oval Square Flat and Edging Diamonds to Square Slabbing Diamond 


MERCHANT MILL ROLL DESIGN 


483 



Fig. 98. Methods of Reduction Used for Roughing Rolls in Merchant Mills. 
































484 


THE ROLLING OF STEEL 


is found in the necessity for economy. 
The rolls, alone, as maybe surmised from 
what has been said concerning their 
manufacture, etc., are very expensive, 
and a large number of rolls on hand 
means a large investment in something 
that is idle most of the time. Added 
to this feature is the expense of roll 
changes, during the time for which the 
entire mill is closed down. In the elimi¬ 
nation of roll changes much depends on 
the way the orders are scheduled. This 
point should, therefore, always be con¬ 
sidered in making up the mill schedules, 
and is a problem to be solved in making 
up promises of delivery for small lots. 
As an example of how scheduling is 
done, the system employed at the Upper 
and Lower Union Mills at Youngstown 
is explained. 

Making Up Schedules—The Order 
in the Office: Upon receipt of the large 
buyers’ schedule, which usually comes 
about the middle of the month for the 
following month, the respective schedule 
clerks pick out from the files the index 
cards corresponding to the buyers’ 
schedule and file them in a desk file. At 
the same time all those index cards with 
promises on them for the next month are 
taken out and put along with those 
already in the desk file. In addition to 
these the oldest index cards are also 
worked in whenever it is possible. Before 
these index cards are put in the desk 
file, however, they are checked against 
the book,orders for mistakes, etc., and 
the date of order. By this means it is 
known that the item is either in the 
desk file or out on the mill. The 
index cards in the desk files thus represent 
all the promised and scheduled material 
for the next month. From these files 
the schedule clerks make up rollings 
for their respective mills. For this 




CO 

3 


T3 

C 

2 

So 


* 







Planishing Pass Strand Pass 2 Pony Roughing Pass 3 Pony Roughing Pass 1 
















MERCHANT MILL PRODUCTS 


485 



Front View 

Fia. 90. Sketch Showing Passes and Location of Same in Rolls for Window Sash Section. 























































































































































































































































































































486 


THE ROLLING OF STEEL 


purpose index cards showing the different sizes of sections and grades 
of steel on the schedule are also kept. To keep the scrap loss 
on the mill to a minimum the longest exact cuts are put first, the exact short 
lengths come next and after these are placed the common lengths. There¬ 
fore, when shearing the long exact cuts, the short ends may be sheared into 
the shorter lengths; and if a long piece comes at the end, it may be sheared 
to one of the long common length cuts. The amoimt of tonnage to a roll¬ 
ing varies with the mill and the section being rolled. In making up a 
rolling it must be watched that a car load of material is checked out, so 
material will not have to be piled. If there is not enough material at 
either Upper or Lower Mills to make up a car load for the customer the 
products for both Upper and Lower for that customer are combined to 
make up a car load, the shipping offices having previously decided at 
which plant to start the car. Sometimes an order will be transferred from 
one mill to the other so as to prevent this condition. In this case, the 
order is transferred by making out two correction slips. One of the slips 
goes to the one mill telling its foreman to cancel the order that is to be 
transferred, and the other goes to the other mill telling its foreman to 
reinstate the order mentioned. The correction slips are made out in 
triplicate form, a copy of each remaining at the order department, and the 
original and a copy of each going to the proper shipping office where the 
original is returned and noted to the order department, while the copy is 
kept on file at the shipping office. The schedule clerk in the order depart¬ 
ment keeps a record of the orders he sends to the mill order clerk for each 
mill and from time to time checks up with him regarding the amount of steel 
on hand. After a rolling has been made up, the index cards are hectograph- 
ed and three copies are made. These copies are known as mill order sheets. 

The Order at the Mill—Size of Billet or Bloom: The original index 
cards, together with the copies, are sent to the mill order clerk, who gives 
the index cards to the shipping office, keeps one copy of the mill order, 
and sends the other two to the mill foreman. These should be sent over 
to the mills at least twelve hours before they are to be put out on the mill, 
so that the foreman will have time to figure out the weight billet required 
and to order the steel from the mill stocker. Due to various influences, 
however, the orders are often sent out only a few minutes before they are 
put on the mill. In figuring out the billet or bloom required for the order, 
the foreman figures the length to which he can run the material on the 
cooling bed and obtain multiple lengths of the cut ordered, taking into 
consideration both the length of the hot bed and the mill practice. He 
then multiplies the mill length that the bar is to be rolled on by the weight 
per foot of the section, which gives him the weight billet or bloom needed, 
not allowing for scrap or furnace loss. About 10% is added to most orders 
to offset furnace and scrap loss. However, this factor changes with the 
section and the cut. Common length cuts on large material requires some¬ 
times as little as 5%, but on the other hand light material, such as crescents, 




MERCHANT MILL PRACTICE 


487 


on which the cut is exact and the inspection rigid, the amount added will 
sometimes be as high as 25%. In figuring the weight billet required, the 
width of the furnace must also be taken into account. Blooms for common 
grades of steel are furnished by the Ohio Works in different weights, 
increasing by fives from one hundred to three hundred pounds, while bil¬ 
lets, unless otherwise requisitioned, are furnished in lengths of thirty feet. 
After figuring the orders, the mill foreman makes out a steel order with 
two carbon copies. The original is kept on file; one of the copies is given 
to the stocker, who sees that the billets or blooms are cut to weight and 
delivered to the heating furnaces; and the other is given to the steel yard 
foreman, so he can check the same against his records. The orders are 
then given to the shear foreman and the roller, the size of the section 
being marked on the margin of the latter’s sheet in large clear figures in 
order to eliminate any possible error in size. When the shipping office 
receives the index card from the mill order clerk, the card is blue- 
penciled showing date the order was received from the order department. 
It is then returned to the mill order clerk who files it until he places the 
order on the mill. The card is again given to the shipping office when the 
order is placed on the mill, and, this time, the date the order is put on the 
mill is marked with black pencil. A shipping clerk looks up the book 
order and marks the index card with the information as to whether the 
material is to be piled or loaded into a railroad car, which is dependent 
upon how much material for that customer is being rolled. The marked 
index card is then filed according to size and section. 


SECTION IV. 

ROLLING PRACTICE IN MERCHANT MILLS. 

The Roller: While the roll designer is indispensable, and the roll shop 
represents the heart of the rolling mill plant, much depends on the roller. 
He must be a man with not a little ability, capable of exercising good judg¬ 
ment at all times and possessing considerable practical knowledge. With 
closer and closer rolling tolerances being demanded by the customer and 
larger tonnages required, due to the rapid growth of the steel industry, 
the roller has been placed in the difficult position of meeting rigid speci¬ 
fications and breaking tonnage records at the same time. This achieve¬ 
ment appears the more remarkable when it is recalled that all the training 
the roller gets is along practical lines. His only school is the school of 
experience in which a man is never graduated. It is manifestly impossible, 
therefore, to explain satisfactorily the knowledge of the roller or the method 
of his working. The best that can be done is to point out some of the 
duties of the roller and mention a few of the precautions he must 
observe. 

Precautions in Rolling: In a word, it is the duty of the roller to see 
that the rolling is properly done and the material meets the specification 




48S 


THE ROLLING OF STEEL 


as to size, shape and freedom from rolling defects. In building up rolls 
in the housings care should be taken by the roller that they are plumb, 
square and level. If the rolls are not plumb, i. e., if the line joining their 
centers is not straight and perpendicular to a horizontal, the bar will not 
deliver properly, and trouble with the guides will undoubtedly occur. This 
condition is often caused by bearings wearing out or poor babbitting 
originally and can only be remedied by changing bearings or, in some 
instances, by the use of side liners or wedges. Should the rolls be out of 
square, that is, if the center of the pass in the top roll is not directly above 
the center of the pass in the lower roll, the bar will be out of square and 
will twist as it issues from the rolls. In order to square up the rolls, set 
screws which work against the bearings are provided on the sides of the 
housings, and thus the rolls can be thrown either one way or the other as 
the case may demand. The directions for correcting this fault are, in the 
language of the mill, “Follow the twist,” and the top roll is always thrown 
over in the direction that the bar is twisting. In the event that the rolls 
are not level, that is, perfectly parallel, more work will be done on one side 
than on the other, with the result that the bar will not deliver straight 
but will tend to curve around toward the side on which there is the lightest 
draft, due to the other side being elongated the more. This condition may 
be remedied either by the use of liners or by operating the screw down at 
the proper side. Guides and guards play a most important part in rolling 
mill practice, and the proper setting of these is one of the roller’s most 
important duties. His assistants may set the guides for the strand and 
planishing rolls, but those for the finishing pass are always set by the 
roller. Entering guides on the finishing passes are usually closed, the 
inner end being so shaped that it will provide sufficient bearing to hold the 
piece up in correct position while entering the pass. If the guides are not 
set properly, the bar will not be formed rightly. Especially when rolling 
rounds, the entering guides should be tight in order to. hold the oval in a 
vertical position, for a leaning to either one side or the other will produce 
a high and a low shoulder on the finished round. The position of the 
guides on the delivery side is also most important, for since the bar has a 
tendency to follow the smaller roll diameter, the guide against which the 
bar is thrown must be watched most carefully. If the bottom roll is the 
smaller, then the bottom guide should not be placed too low, for the bar 
coming out would have a tendency to follow the roll down for a short space 
before striking the guide. This would cause an up and down kink, or a 
buckle. A short guide has the same effect. 

* 

Rolling Defects: In addition to working for the proper size and finish 
on the bar, the roller must watch for such surface defects as overfills or 
pinches, underfills, buckles, slivers, seams, laps, firecracks, roll marks, etc. 
Overfills or pinches must be watched especially in changing from Bessemer to 
open hearth steel, as the latter has more of a tendency to spread than does 
the former. When overfills occur, the amount of stock entering the pass 













MERCHANT MILL PRACTICE 


489 


that is producing the overfill must be reduced by adjusting the rolls in 
preceding passes. Underfills are corrected by reversing these operations. 
Buckles are sometimes caused by worn out pinions. Slivers can be 
produced from many causes at the blooming mill or by the bar shearing 
against a guide or collar of a roll at the finishing mills. The former 
condition cannot be corrected by the merchant mill roller, but the latter 
can be eliminated by a proper adjustment of the proper guide or by reducing 
the stock in the bar which is shearing against the collar. Seams are defects 
in the steel that cannot always be corrected by the finishing mill, as they 
are usually formed in the bloom or the billet. A lap is caused by an overfill 
or fin being formed and then being doubled over and rolled down in the 
subsequent passes. This defect can be controlled by the roller by going 
back to the stand at which the overfill was formed and reducing the stock. 
Firecracks are caused by the rolls becoming overheated and cracking on 
the surface. These cracks cause corresponding small elevations on the 
surface of the bar, which in some instances condemn the material. When 
this defect appears, the roller “moves over” and uses a “clean” pass. The 
same procedure is followed when any other roll mark appears on the finished 
bar. Roll marks occur at equal intervals along the bar and signify that 
there is a piece out of the roll or that the roll is marking the bar with each 
revolution in some other manner. 


Two Different Finishes on bars are furnished at the Youngstown 
plant, namely, common and special. The special finish has a smooth, highly 
polished appearance and is produced by cleaning all scale from the bar at 
the planishing stand and finishing at such a low temperature that no more 
scale will form on the surface. 

The Special Finish is produced on rounds by holding the square back 
before entering the planishing, until a dark scale has formed and then bend¬ 
ing the bar with a pair of special tongs as it enters the rolls. A stream of 
water plays directly upon the bar as it enters both the planishing and finish¬ 
ing passes, and scouring blocks covered»with emery powder are used on the 
finishing stand in order to keep the pass clean. Material requiring the 
special finish is always rolled ahead of the common orders of like sizes, 
so that a clean pass will be available. Flats are not scraped in order to 
furnish the special finish, but are simply held back until their temperature 
reaches the critical range before entering the planishing pass. On large 
flats, water is used on the bar as it issues from the planishing, so that the 
scale thus broken up will be removed and not be rolled into the steel. 
Another reason for using water on large sections is that they will be delivered 
to the hot beds below the scale forming temperatures. Cooling is un¬ 
necessary, however, on small sections, such as crescents, half ovals and 
ovals, as these lose their heat so rapidly that even water is not used directly 
on the bar. A scraper, located at the entering side of the finishing stand, 




490 


THE ROLLING OF STEEL 


» 

is the only means used for producing the special finish upon these sections. 
Due to the fact that scale adheres more tenaciously to open hearth than 
it does to Bessemer steel, the latter takes a much better finish than the 
former. Open hearth steel will become smooth but does not have the 
highly polished appearance of Bessemer steel. It is the roller’s experience 
that Bessemer screw steel takes the best finish of any grade turned out at 
the converting mills. This grade not only takes a smooth finish but some 
times gives a mirror-like surface. It should be observed that the holding 
back of the bar to produce this finish may so retard the rolling as to 
decrease seriously the total output of the mill. 


SECTION V. 

SHEARING AND BUNDLING MERCHANT MILL PRODUCTS. 

The Methods of Shearing and Bundling vary at the different plants 
according to equipment, product, location, etc., and no description of value 
yet general enough to be descriptive of all plants can be given. As the 
greatest variety of sections are produced at the Youngstown Upper and 
Lower Union Works, a brief outline of the methods and practices at this 
plant may be found of value. 

Duties of the Shear Foreman: The man who is responsible for 
completing orders, i. e., for the shearing and the bundling on each mill, 
is the shear foreman. His force is usually composed of a shearman, a 
gauger, a push-up, a pull-up, and two or more bundlers. The first duty 
of the shear foreman is to keep the different orders, heats and turns separate 
on the cooling beds and to tag each item on the truck properly. The 
different lots are kept separate on the trucks by means of bands. A load 
sheet is made out for each truck, shewing the material loaded on it. When 
the truck is full, it is the duty of the shear foreman to notify the yard master 
or dinkey engineer to pull the load to the warehouse, or shipping room. 
It is also the duty of the shear foreman to set the gauge for shearing the 
material, allowing a certain amount for contraction during the cooling 
process. The amount allowed on the smaller mills is one-fourth inch over 
or under for every five feet, but this amount varies with the size of the bar. 
When material is to be bundled, the weight of the bundles is nearly always 
specified, but when instructions are not given, it is the mill practice to 
bundle material to weigh 100 to 150 pounds per bundle. By multiplying 
the weight per foot of the section by the cut and dividing the product into 
the weight of a bundle, the shear foreman determines how many bars to 
put in a bundle; but in order to check himself up he weighs the first bundle 






MERCHANT MILL PRACTICE 


491 


of each new cut. It is the object of the shear foreman to put the same 
number of bars in each bundle, as this not only makes all the bundles of 
uniform weight but facilitates the recounting of a bar order by the men in 
the warehouse. On some mills the head bundler counts the bars, while on 
other mills tally boys are employed. In bundling material up to twelve 
feet on domestic orders only two “Carnegie” bands are used. Up to twenty 
feet three “Carnegie” bands are used, while four are used on all cuts twenty 
feet and over. 

Bundling Export Material: On export orders, the weight of a bundle is 
always specified, the weight usually being 112 pounds, so that twenty bundles 
make one gross ton. On lengths up to fourteen feet three bands, marked 
“Carnegie, Made in U. S. A.,” are used. From fourteen feet to twenty-two 
feet four bands are used, and one additional is putonfor every sixfeet above 
twenty-two feet. On all export orders, special “export” tongs are used, 
as with these tongs the material can be tied very securely. The following 
rules apply to the handling of export orders: All orders must be complete. 
All bundles, excepting the last, must contain the same number of bars. 
All bundles are to be tightly tied with “export” tongs whenever possible, 
and bands used are to be in accordance with instructions on orders. These 
instructions may call for export bands, plain bands, or wire. All export 
material must be loaded on separate trucks, except in very small orders, 
or when the material is needed by the warehouse to complete an order 
hurriedly. All trucks containing any export material must bear a red export 
tag, and all excesses are to be loaded on trucks but kept distinctly separate, 
tagged plainly as “Excess,” and showing order number, customer, size, 
etc. The name of the man who is responsible for tallying and bundling 
is placed on the tag, and all orders are very plainly tagged, the tags being 
so placed that there is little liability of their being torn, pulled off or made 
illegible. On all trucks are placed load sheets which are put in oiled 
envelopes so that weather conditions can not destroy, or blur, the writing. 

Special Bundling: Some material, such as ovals, tees, etc., often 
specify “Tie with wire,” while other orders, especially for large material, 
specify the material to be shipped loose. A good many orders, such as 
hoops, flats, rounds, squares, and small nut steel, are often ordered coiled. 
This is accomplished by means of coilers with adjustable pins so that coils 
of different diameters can be furnished. The usual diameter, however, is 
twenty-four inches. These coilers are located at one end of the hot bed 
or at some other convenient point according to available space. All coilers 
are electrically driven. 

Handling the Material in the Warehouse: When the truck load of 
material arrives at the warehouse, the pile-boy takes the load sheet into 
the office and gets the corresponding index cards, because the load sheet 
shows only the order number, size, cut, grade of steel and remarks. The 
index cards show customers name and loading and shipping instructions. 





492 


THE ROLLING OF STEEL 


As each item is weighed off from the truck, it is entered on a weight sheet 
by a weigh-man and checked off on both the index card and load sheet. 
If the index card is marked “Car” a car is started for that customer, if 
this has not already been done, and material is so loaded. If index card 
is marked “Pile” the item is piled and so noted on the weight sheet. One 
weight sheet is made out for each truck load, and when this car has been 
weighed off, the sheet is checked off on the car card, of which there is one 
for each car, and returned to the office. Here the weight sheets are checked 
against the order books. Memorandums are made out for the items that 
have been piled so that these can be given out to the weighmen when a 
car load has been started for the customer. When an item of an order is 
under weight or short in number of pieces, the shortage is discovered by 
a weekly survey of the order books by a clerk in the shipping office, who 
makes out a reindex card for the shortage and notes the date made out 
with blue pencil on both the reindex card and the book order. If, however, 
there is a chance to get the item on the mill immediately, the book order 
and the index card are black penciled. A rolling order is made out from 
the reindex card and hectographed, after which the index card and three 
mill order sheets are given to the mill order clerk. He returns the reindex 
card to the shipping offices, and if he does not have the grade of steel in 
stock, he has to make out a requisition for it, the procedure then being 
the same as for ordinary orders. 

9 

Straightening: At the lower mill, straightening is done by the Labor 
Department, machines for this purpose being located at three different 
places. These machines are of the seven roll type, the rolls being built 
up in a casting similar to roll housings. Four rolls are below and three 
above, the bar passing between in grooves which are designed to fit each 
separate section. On account of the vast amount of tire and window sash 
sections rolled at the Upper Mills, the straightening is under the juris¬ 
diction of a special department for that purpose. Angles and sash sections, 
molding tees, and mud guard sections are straightened at the mill, there 
being a straightening machine located at each mill where such material 
is rolled. Round edge tire, however, is straightened in the tire house, 
where two straightening machines of a new type are located. These are 
more flexible than the old type and are more easily adjusted to the various 
sizes. 

Invoicing: After the cars have been loaded, the car cards are taken 
into the shipping office, and from these, invoices are made out. The original 
office copy of the invoice, which is made out in the shipping office, is sent 
to the order department where it is carefully checked against the book 
order, the number of bars or bundles and tonnage being entered on same. 
The invoices are next given to a clerk who enters all detailed information 
on a “recap’’ sheet. The credits for the various sections and sizes are also 
entered under the proper headings on a “credit recap sheet.” 







MERCHANT MILL PRACTICE 


493 


<- SECTION VI. 

/ i 

INSPECTION DEPARTMENT OF A MERCHANT MILL PLANT. 

The Inspection Department makes all physical tests and keeps 

records and samples of the various sections. One of the duties of this 
department is to inspect and accept or reject all special steel before being 
rolled into finished product. Check analysis is made of all steel requiring 
the same, and a close inspection of all material when being rolled is provided 
for. All special steel ordered from the semi-finishing mills must pass 
inspection by this department. Approval or disapproval of material is 
based upon chemical analysis and surface conditions. Only very low 
limits for the various impurities are allowed on special steels, and the 
inspection is very rigid. Consequently, any heats not falling within the 
requirements must receive special attention. Much in the way of good 
judgment is required to dispose of such heats satisfactorily. Usually, the 
department will endeavor to consult the customer before permitting an off 
grade heat to be rolled as originally planned. Certain orders require the 
ladle analysis to be checked before being rolled into the finished bar. Orders 
requesting check analysis are held in the yard until drillings from 
the billets are analyzed. If this analysis shows that the composition of 
the steel is as ordered, the steel is rolled on the order for which it was 
originaHy intended. If the check analysis does not practically agree with 
the ladle analysis, the steel is applied on a less particular order. Check 
analysis may also be made on finished material. Some orders require that 
the steel be inspected for surface defects before rolling. In such cases 
each billet is carefully examined to detect any slivers, seams, checks, or 
faulty shearing that may occur. Billets found to be defective are chipped 
and put into condition for rolling if at all possible. When orders specify 
physical requirements, it is then the duty of this department to supply such 
chemical specifications as will fulfill the physical requirements. 

Another Function of this Department is that of mill inspection, 
which is one of most importance. In this capacity the department acts 
as a check upon the rolling. Mill inspection requires one man on each mill, 
devoting his entire time to gauging and watching for faulty steel. Sections 
not fulfilling the prescribed measurements are either held for further 
inspection or thrown out as scrap. The rollers as well as the inspectors, 
have the given dimensions and tolerances. The inspectors check the rollers 
and inform them of any faults that the rollers themselves have not already 
detected. In case an inspector does not accept steel as rolled, and the 
roller continues to make the section, the inspector signals for the depart¬ 
ment superintendent and lays the case before him. If the fault cannot be 
remedied, and it is known the customer will not accept the steel as rolled, 
the mill must go off the order. The defects watched for most closely 
depend upon the section being rolled. Accurate size applies to all sections. 




494 


MERCHANT MILL PRODUCTS 


For the more complicated sections templets are furnished. Usually one 
exact and one full templet is made. For gauging rounds, squares, flats, 
etc., only a gauge and micrometer is used. Readings on the micrometer 
are accurate to .001 inch, while on the gauge one-sixty-fourth inch is about 
the most exact reading that can be determined. Other tools used for special 
purposes are squares and steel tapes. The square is used to detect diamond¬ 
ing in certain instances where each surface must be at right angles to the 
adjacent one. The tape is used when inspecting clip sections, to determine 
the regularity of the impressions that are rolled on the bar. 

Surface Defects: The inspector is responsible for the detection of 
surface defects. These may appear as buckles, kinks, overfills, underfills, 
slivers, laps, seams, or burned steel. While the nature and causes of these 
defects have already been more or less fully explained, the following resum6 
of defects most likely to occur in merchant mill rolling is appended for 
ready reference: 

Buckles and Kinks: A bar, when delivered from the finishing rolls, 
may be wavy, either up and down or sideways. The former is known as 
a buckle, while the latter is a kink. These defects are more injurious to 
some sections than others. However, all sections should be rolled as free 
from buckles and kinks as possible. Crescents have a tendency to buckle, 
consequently they must be watched closely. 

Fins: If a bar has a fin or extra amount of metal at the sides where 
the finishing rolls come together, the bar is said to be over-filled. Bars 
rolled for cold drawing must be free from over-fills, for these draw into 
laps. On the other hand, in order to get perfect corners on half ovals, a 
well known file manufacturer requests a small overfill at the edges. 

Underfills: When a bar is scant in certain dimensions or when it is 
not completely filled out, the bar is said to be underfilled. This defect 
sometimes appears on rounds and channels. 

Slivers are loose pieces of steel rolled flat on a bar. They may be 
present on the billet or be caused by faulty shearing, or incorrect entering 
of the bar in a closed pass. Slivered steel is thrown out as scrap and seldom 
held for further inspection. 

Laps: If a bar is given a pass in the rolls after an overfill has been 
produced, a lap usually results. This defect is especially liable to occur 
with skelp, hoop and cotton-tie. Faulty ingots and poor rolling at the 
semi-finishing mills also cause laps. 

Seams: Steel must be inspected carefully for seams, a surface defect 
always difficult to detect. A seam is a crevice in steel that is closed 
up but not welded. Seams are caused by blow holes and cracks in the 
ingot, as well as faulty methods of rolling. They render steel unfit for 
hardening. 








INSPECTION 


495 


Burned Steel shows up in the finished bar in the form of rough, checked 
edges. Burned steel is ruined, and the only alternative is to scrap it. 

Roll Marks: Sometimes a roll is nicked, or a piece breaks off the 
roll, resulting in periodic impressions along the bar. The defect is 
corrected only by a new pass. Fire cracked rolls make similar impressions. 

Finish: The finishing pass, if worn, does not give a smooth surface, 
consequently when the surface of a bar is not up to the standard in finish 
the pass must be changed. This defect is especially objectionable when 
rolling cotton tie, hoop, skelp and sections requiring the special finish. 

Pi pe: The inspector must watch the sheared ends of bars for piping. 
This defect, however, is usually detected at the billet shears before the 
steel is charged. 

Testing for Defects: Tests for detecting some of these defects are 
employed by the inspectors. The tests most commonly employed for this 
purpose are the upset, forging and pickle tests. The upset test consists of 
heating a short sample piece in a forge or furnace and upsetting under a. 
hammer. This is a severe test and readily shows up seams and laps. For 
forging tests, a bar about ten inches long is heated and forged along the 
longitudinal axis of the bar, which is then nicked and broken. Piped steel 
is readily detected by this treatment, as the forging opens up the pipe. 
The upset test is more often used than the forging test, especially when 
rolling forging steel. The pickle test consists of immersing for a few 
moments short pieces of the material in dilute sulphuric acid. The acid 
removes the scale from the bar, exposing to view and exaggating any surface 
defects that may be covered by the scale. Tests pieces of hoop and file 
steel are pickled. At the Youngstown Upper and Lower Union Mills all 
forging tests must be turned in for the personal inspection of the depart¬ 
ment superintendent, while the pickle tests are saved at the test house 
for six months before being discarded. With hoop, the pickled samples are 
held in a vise and the edges turned over with a hammer. This distortion 
of the metal opens up any laps that may be present. On special section 
the inspectors are required to save samples every half hour. These are 
bundled together, properly tagged, and sent to the test house, where they 
are saved for three months. 

Other Duties of Inspectors: Besides inspecting material for surface 
defects, the mill inspector must check the bundling requirements as well 
as the length of cut. This practice reduces bundling and shearing errors 
to a minimum. An hourly report with carbon copy is made by each, mill 
inspector. This report shows the variations in size of the bar for each 
hour of the day. Notations are made of any steel held up and the cause 
of the same. These reports must be delivered to the inspection office at the 
end of each turn. Since the different sections are gauged differently, the 
make-up of the reports will differ accordingly. 




496 


MERCHANT MILL PRODUCTS 


Manner of Gauging Different Sections: Rounds are gauged on four 
diameters, distinguished at the mill as top-and-bottom, sides, and high and 
low shoulder. By top-and-bottom of a round is meant those two surfaces 
subject to compression in the finishing pass, and by sides is meant the 
points opposite the clearance between the rolls in this pass. The shoulders 
lie between these two diameters. The longer of the shoulder diameters 
is called the high shoulder, the shorter the low shoulder. Three samples 
are taken from each bar gauged, namely, front end, middle and last end. 
These samples are taken at the shears as the original bar is being cut into 
the lengths ordered. The top and bottom of a round may be distinguished 
from the sides by the way the scale is broken along the sides. If an overfill 
occurs, it shows also on the sides of the round. Usually, the ends of a mill 
length of a round are slightly overfilled. Flats, squares and nut steel are 
gauged for width, thickness and diamonding, but only the variations in 
width and thickness are reported. Cotton-tie, hoop, and skelp are reported 
for width and gauge thickness. Special sections are usually gauged by 
means of templets, but certain overall dimensions are generally given on the 
report. A sketch is sometimes made and the important dimensions lettered. 
The hourly variations for these dimensions are then inserted under the 
proper heading. Clip-iron, box-strap and bit-mouth are peculiar sections 
requiring special attention for gauging, and the various dimensions must 
be watched to get the section uniform. Inspectors at the cotton-tie mill 
have special duties to perform. They must get from each buckle machine 
every half hour a sample, which must be properly tagged and taken to 
the department superintendent for personal inspection. They are required 
to weigh ten bundles of cotton-tie every half hour and to post the weight 
on a blackboard in plain view of the roller. Concrete bar is rolled to 
weight, and inspectors must check the weights of the shear foreman. If 
for any reason an inspector is not willing to take the responsibility of passing 
slightly defective bars, the trucks loaded with such steel are marked with 
green tags, signifying, “hold for further inspection.” This steel is examined 
by the assistant chief inspector, who either scraps the entire lot or details 
a specially instructed inspector to sort the good from the bad. Uses for 
which steel is rolled, as well as customers’ claims, offer guides as to what 
defects a customer can accept. 





CIRCULAR SHAPES 


497 


CHAPTER X. 

CIRCULAR SHAPES. 

SECTION I. 

SOME GENERAL FEATURES PERTAINING TO THE ROLLING OF CIRCULAR SHAPES. 

• 

The Rolling of Circular Shapes presents one of the most interesting 
studies of the rolling mill industry, because it is the latest development 
in rolling, and, though the idea of rolling wheels originated in Europe, it 
is in America that the art has been most highly developed. The beginning 
of this branch of the industry dates from the year 1903, when solid rolled 
steel car wheels were first used under freight cars. The use of such wheels 
resulted from the introduction in 1896 of all steel freight cars, which on 
account of their increased weight and great carrying capacity required 
a stronger and tougher wheel than any that had been made up to that time. 
It was to meet this requirement that Mr. Charles T. Schoen, who was the 
pioneer in the manufacture of all steel cars, perfected the mill, which now 
bears his name, for rolling these wheels. Later on, Mr. Schoen’s method 
of preparing the steel, which will be explained later, was much improved 
by the Carnegie Steel Company, who purchased this mill in 1908. Con¬ 
sidered from the standpoint of circular shapes in general, the Schoen mill 
has the one drawback of a very limited product. Being designed for one 
particular purpose, it can roll only car wheels, or wheels of that class, and 
of these it is limited to wheels between thirty and forty-two inches in 
diameter. While wheels as small as twenty-eight inches in diameter have 
been made on this mill, these smaller sizes are rolled with much difficulty, 
due both to the form of the rolls and the manner of rolling. For forming 
wheels less than thirty inches in diameter the Carnegie Steel Company has 
found that the forging press gives the most satisfactory results. 

x 

Preparing the Blanks: The circular shapes all require a round blank 
to start with. Mr. Schoen originally sheared his blanks from slabs with 
a specially constructed punch-like shear, the further work being then com¬ 
pleted in much the same manner as it is done today. But this method 
had the serious fault of producing a wheel in which the line of segregation, 
or pipe, if any were present in the slab, was located diametrically across 
the wheel and terminated at both ends in the tread. From what has already 
been said about pipes and segregated steel, it is easy to see how this location 
of the segregated area might develop defects at these two opposite points. 
As has already been intimated, the Carnegie Steel Company was responsible 
for bringing about the correction of this fault, which is removed by locating 




498 


THE ROLLING OF STEEL 


the segregated line at the center and at right angles to the radii of the 
wheel, where the faulty material may be punched out for the bore. It is 
evident that the line of segregation may be so located in any one of three 
ways, namely, by casting the blanks individually, by cutting the blanks 
from round or hexagonal ingots, and by rolling the ingots into a round 
bloom from which the blanks may be sheared or sawed. All these methods 
are in use by the various manufacturers of wheels, but it would appear 
that the second and the third method should produce the best wheel, because 
more work is put on the steel. The third method is the one used by the 
Carnegie Steel Company. The round blooms for the Schoen mills are 
rolled at present on a twenty-eight inch bloomer at Homestead. Here a 
22" x 22" ingot is slowly and carefully reduced in from twenty-one to thirty- 
one passes to a round bloom, eleven or fifteen inches in diameter for forged 
products, or fifteen inches in diameter for all wheels that are to be rolled 
at Schoen. From the blooming mill, the bloom, is delivered to a patented 
shear, known as the Slick shear, which is so located, in conjunction with the 
delivery table and the manner of rolling, that first cuts are made from that 
part of the bloom corresponding to the bottom or butt of the ingot. This 
first cut, usually about 5% of the ingot, is just sufficient to square up the 
butt end of the bloom and is always discarded. The remainder of the 
bloom, excepting the discard for pipe, is then cut into lengths to give the 
proper weight of metal required in the wheel, with an allowance of ten 
pounds over or under weight, and, if requested, each cut is hand stamped 
with a letter to indicate its position in the ingot, starting with A 
for the first cut next to the discard at the top of the ingot. Cut A, 
and often cut B, also, is used in making wheels for the use of the Steel Cor¬ 
poration only. In any case the total discard, which may include both A 
and B cuts, on wheels to the customer is never less than 25%, which amount 
is sufficient to insure sound steel in the wheels. For marking the heat 
number and weight of cut, the shear is provided with a stamp mounted 
on the revolving clamp for the shear knife, so that each disc, or blank, is 
plainly stamped with its heat number and weight. From the shears the 
blanks are taken to a shipping yard, where they are carefully inspected for 
surface defects, which are cut out by means of pneumatic chipping tools. 
Such of the blanks as pass this inspection are then sent to the mills to be 
worked into wheels. 


SECTION II. 

THE CARNEGIE SCHOEN METHOD FOR MANUFACTURING STEEL WHEELS. 

The Carnegie Schoen Method: At the Schoen plant, which consists 
of three separate units, the finished wheel is produced in several stages, 
the number of which depend upon the kind of wheel, the unit in which it 
is made, and the working conditions of the heating furnaces. Upon receipt 
of the blanks at the plant, they are check weighed, and the heat number 
of each blank as well as the letter indicating its position in the ingot are 







CIRCULAR SHAPES 


499 


all recorded in the form of a serial number. The blanks are then charged 
in order into a reheating furnace, where they remain for about two and 
one-half hours. In the older units, mills number one and two, the reheating 
furnaces are all of the regenerative type and use producer gas; but in the 
most recent mill, or number three, the first furnace is of the continuous 
type, the bottom of which is inclined sufficiently to cause the blanks to 
roll down from the feeding end as rapidly as they are removed at the drawing 
end. This type of furnace heats the discs very slowly and gradually, 
because it is intended merely to give the discs a preliminary heating, and 
its temperature is therefore low. At the drawing end, the temperature is 
maintained at about 800° C. After being subjected to this preliminary 
heating, the discs are transferred to a regenerative furnace for the final 
heating previous to forging. When the discs have reached the proper 
temperature, they are withdrawn from the furnace and taken to the forging 
presses where each is forged to a shape resembling that of the finished 
wheel before dishing or coning. As to dimensions, this forged blank is 
from four to five inches under size in diameter, some three-fourths inch 
over size in that part of the web near the rim, somewhat oversize, also, 
in depth of rim, a little oversize in width of rim, but of correct or slightly 
full size in the hub and a small part of the web next to the hub. 

Forging the Blanks—First Method: The forging may be done in 
one heat or two heats and on one press or on two different presses. When 
two heats are used, two presses are usually employed for the forging. In 
this method, the disc is cleaned of scale on its two ends and then placed 
vertically in the first press, where it is first perfectly centered by two 
arms which engage it from opposite sides of the press and so support it till 
the top die has descended upon it. In this press the bottom die corresponds 
to the outside face of the wheel while the top die is plain, but may be slightly 
convex to cause a radial flow of the metal in taking the shape. The pressure, 
applied in successive steps by means of accumulators and intensifier, starts 
with about 700 pounds per square inch, then increases to 2500 pounds and, 
finally, to as much as 4500 pounds per square inch, if needed. At the begin¬ 
ning, the scale is cracked from the disc and falls into the bottom die, from 
which it is blown by means of a steam jet, in order to avoid pitting the 
surface of the blank. This pressing is, in itself, a severe test upon the 
metal, and any flaws, such as seams or cracks, are sure to be exposed, 
although they seldom occur. When such flaws do develop, the blank is 
scrapped at this press. The perfect blanks are now placed in a second 
reheating furnace, where their temperature is equalized and brought again 
to the forging point. When these conditions have been attained, the blank 
is cleaned of scale and placed in a second press, in which the top die con¬ 
forms to the shape of the inside face of the wheel. Before applying the 
pressure, a little fine coal is thrown on the bottom die and upon the blank 
to prevent the dies sticking and to keep their surfaces smooth. After this 
forging, the blank is placed in a third press, where the bore is punched. 





500 


THE ROLLING OF STEEL 


During the punching, the hub of the wheel is supported in neatly fitting 
dies in order to avoid forcing this part of the wheel out of shape. 

In the Second Method of Forging, the press is provided with the two 
top dies mentioned in connection with the two presses used in the first 
method. These dies are mounted upon a sliding frame in such a manner 
that either may be brought at will beneath the piston of the press, thereby 
dispensing with the first forging press and permitting the forging to be 
accomplished in one operation when the conditions are favorable. Thus, 
if the blank is at a temperature sufficiently high and is evenly heated through¬ 
out, the second top die, conforming to the inside of the wheel, is brought over 
the blank, and the forging is completed in a single stage. If the conditions 
are such as are likely to cause an uneven flow of the metal, which results 
if the blanks are unevenly heated, the plain die is used first, then the inside 
die is moved into position and the pressure applied, thus forming the blank 
in two stages, but on a single heating. The bore is then immediately 
punched as in the first method. After the forging, by whichever method 
that may have been used, and the punching of the bore, the blank is placed 
in a reheating furnace where it remains until it has reached the proper 
temperature for rolling. 

The Rolling Mill: The two older mills are very similar in every detail 
of their construction, but in the number three mill, which made its first 
trial rolling June 5th, 1917, a few changes looking toward an improvement 
in construction over the older mills have been made. For this reason this 
mill, rather than either of the older ones, will be described. This descrip¬ 
tion is, however, made rather brief, for the mill, itself, is a somewhat 
complicated piece of machinery, as the reader will surmise when he is told 
that seven rolls play upon the wheel at one time during the rolling. These 
rolls consist of one tread roll, two web rolls, and four (2 sets) rim rolls, 
and are supported, together with all their bearings, pinions, or gears, 
adjusting screws, levers, etc., in one pair of horizontal housings, which are 
large steel castings and placed'one above the other. The bottom housing 
lies directly upon the mill foundation and forms the support for the rolls 
and for the top housing some four feet above it. The housings are held 
apart by suitable pillars or posts and are bound firmly together by means 
of immense bolts. Between these housings the rolls are located; they may 
be described as follows: The largest roll is the tread and flange roll. In 
form it resembles a wheel, some thirty-three inches in diameter, and is so 
located back near the central point of the housings that, during the rolling, 
it revolves in the same vertical plane as the wheel and bears upon its tread 
from the rear. Its face is somewhat wider than the rim of the wheel and 
is grooved to correspond to the tread and flange. It is friction driven 
and is carried on a slide bearing, so that, by means of a screw, connecting 
the sliding box to a fixture at the rear of the housings and operated through 
a worm shaft and gear by means of a 15 h. p. electric motor located on 



















CIRCULAR SHAPES 


501 



Fig 100. Drawing of Schoen Mill Showing Wheel with Web, Tread, and One Set 
’ Rim Rolls in Position at End of the Rolling Operation. 






























































































































































































































































































































































































































































































502 


THE ROLLING OF STEEL 


top of the upper housing, this roll may be moved backward or forward at 
the will of the operator. Few operators, however, move this roll after the mill 
is once adjusted to roll the wheels of a given size and type. On the opposite 
sides of the tread roll are located the two web rolls. They are about three 
feet in length, lie in a horizontal position and extend inward, so that their 
center lines form angles of nearly 30° with the center line of the mill and 
intersect at a point near the center of the wheel that is being rolled. On 
their front ends they carry the rolling heads, or surfaces, which conform 
to the shape of the wheel beneath the rim, while their rear ends are anchored 
in rotating coupling boxes. Light steel spindles, some five feet in length 
and provided with proper wobblers, connect these couplings to the two 
bevel gears, one of which stands on each side of the mill at the rear. These 
gears mesh into similar gears mounted on the driving shaft of a 750 h. p. 
D. C. motor (500 volts, 1100 amperes, 130 r. p. m.), which, located at the 
rear and on the center line of the mill, is used to drive these rolls. Just 
back of the rolling heads, these rolls are supported in sliding bearings 
which permit of their being spread as desired. The pressure for rolling 
is transmitted to these bearings through radial levers, the long arms of 
which are each attached above the housings to the same screw, so that the 
same motion, but opposite in direction, and equal pressures are imparted to 
the two rolls at the same time. This screw, which corresponds to the 
adjusting screws on ordinary mills, is actuated by means of a 15 h. p. direct 
current motor (220 volts, 64 amperes, 550 r. p. m.). By this means, the 
power of the motor is multiplied many times and is capable, at its maximum, 
of exerting such pressure on the web rolls as to stall the mill. As to the 
relative altitude of these three rolls, they are so placed that their lines of 
contact with the wheel in rolling and the axis of the wheel, itself, all lie in 
the same horizontal plane. The four rim rolls, which are friction driven, 
are located, one pair above and one pair below, the web rolls, so that all the 
rolls lie within an arc of 180° of the circumference of the wheel being rolled. 
These rolls are approximately twelve inches in length and nine inches in 
diameter, and are so placed that the projected axes of rotation of the two 
on either side of the wheel intersect at the axis of rotation of the wheel. 
They are mounted upon sliding frames attached to the front of the mill 
housings. These four frames are moved by horizontal screws connected 
by vertical worm shafts and gears to a common shaft, which extends in 
front of and beneath the housings and is operated by an electric motor set 
some eight or ten feet to the right of the mill, measuring from the side of 
the housings. In this way the spread of these rolls is made uniform. How¬ 
ever, the bottom set of rim rolls, due to the manner of rolling, do nearly 
all the work. An indicator, mounted on the upper horizontal screw attached 
to the sliding frame on the right side of the mill, is in plain view of the 
operator, who is able, by this means, to read the spread of the rolls and thus 
control the width of the rim. These rolls may be so formed that they will 
roll the sides of the rim at a slight angle to the vertical, so that these surfaces 




CIRCULAR SHAPES 


503 


will lie in parallel planes after the dishing, or coning, process. Two shelves 
attached to the housings in front of the tread and web rolls and separated 
by a space a little greater than the thickness of the wheel at the hub, gives 
a support for the wheel, which is mounted on a loosely fitting mandrel 
during the rolling. This mandrel is provided with removable bearings, 
w T hich rest, unattached, upon the shelves, thus leaving the wheel free to 
move forward after the rolls have gripped it. 

The Rolling Process: After the forged blank has attained the proper 
temperature for rolling, it is removed from the furnace and carried to the 
mill with a charging and drawing machine, where it is gripped beneath 
the rim by tongs suspended by a small jib crane standing on the housing 
above the rolls. The wheel, held vertically by the crane, is guided between 
the two supporting shelves, and the mandrel is inserted through the punched 
bore. The crane tongs are then released, and the wheel, resting on the 
mandrel, is pushed back by hand against the tread roll and into the position 
for rolling. The web and rim rolls are then brought to bear on the wheel, 
the latter rather lightly at first. The large driving motor is started, and 
the wheel is made to revolve by the action of the web rolls upon it. These 
rolls, working upon both sides of the web and the under side of the rim, 
force the metal back into the groove of the tread roll with considerable 
pressure, until this part of the wheel has reached the dimensions for which 
the mill is set, or the diameter desired, while the spread of the metal and 
the width of the rim is controlled by pressure applied to the four rim rolls. 
The diameter of the wheel is ascertained by means of a gauge, or caliper, 
one end of which is attached to the tread roll housing,so that it is moved simul¬ 
taneously with this roll, in the same direction and through the same space. 
The other end of the caliper projects in front of the mill, and is provided 
with a hinged arm or pointer, so that it may be raised out of the way for 
inserting the blank or removing the wheel. The end of this pointer is 
curved tow r ard the mill at right angles to its length. At the beginning of 
the rolling, the roller lowers this pointer to rest on the left hand shelf, in 
which position its curved end extends toward the tread roll and is opposite 
its line of contact with the wheel, the pointer having been adjusted so that 
the distance between its point and the tread roll is equal to the diameter 
of the wheel desired. With the rolling, the wheel increases in diameter 
and moves forward on the loose sliding mandrel until a circle on the center 
of its tread comes in contact with this pointer, when the roller stops the 
mill and spreads the rolls for the release of the wheel. During the rolling, 
jets of water are directed against the Surfaces being rolled to remove the 
scale and give a smooth finish to the wheel. In addition to the water, 
a salt jet is also directed against the tread. The actual rolling process 
requires about one minute, so that the maximum capacity of the mill is 
more than 500 wheels per day of twenty-four hours. However, on account 
of the care exercised to assure a high quality of product, these mills are 
operated at only 50 to 00% of their capacity. 





504 


THE ROLLING OF STEEL 


Effect of the Rolli ng: It will be observed that all the work of the rolling 
is concentrated upon the outer part of the web and the rim, where the 
additional refinement due to rolling is most needed. This refinement is 
very marked, as is shown by Brinell tests on sections of the wheel and by 
the visible difference in the structure of the metal between the hub and 
rim. This effect is most marked on the tread, where the hardness of the 
metal and closeness of grain can, no doubt, be considerably increased by 
rolling at low temperature or by chilling the metal by using an increased 
amount of water during the rolling. However, as such practice is likely 
to cause spalling, it is not employed by the operators. As machining the 
tread removes much of this super-refined metal, it would appear that the 
wheel rolled to a finish should be far superior in wearing properties to the 
machined wheel, on first run, at least. Evidence of this fact is seen in the 
increasing demand for rolled to finish wheels for passenger cars, even where 
formerly only machined treads were used. The mill practice on rolled to 
finish wheels is high, but a greater or less number of the wheels require 
machining in order to eliminate slight surface defects or true up the dimen¬ 
sions. 

Punching Web Holes and Coning: After the rolling, the wheel is 
taken on a buggy to a small press, where the web holes are punched, when 
these are required. This press is fitted to punch either two or four holes, 
one and three-fourths inches in diameter, and equally spaced on radii of 
834 934 10, 11, or 12 inches, which are standard radii for all the different 
sizes of wheels. From the punching press, or from the rolling mill, if web 
holes are not required, the wheel is taken to the coning press, being hot 
stamped in transit with the word Carnegie on the inner surface of the web. 
This press is provided with dies which conform to the exact contour of the 
finished wheel, the top die corresponding to the insidp of the wheel. For 
preserving the rotundity of the wheel, the bottom die is surrounded with 
a series of tread blocks in the form of segments of a circle, while the top 
die is similarly provided with a tapered ring to fit over these segments. 
Thus, when the dies are brought together for coning, this ring slips over 
the outside of the segments and forces them firmly against the tread while 
the coning or dishing is being effected. As these blocks leave slight im¬ 
pressions on the tread where adjoining blocks meet, the wheel is turned 
through an arc of a few degrees and again subjected to the pressure, which 
removes all but traces of these marks, except in occasional cases where 
they are unusually deep. Upon removal from this press, the wheel is hot 
stamped with a mill serial number, the heat number and the date, then 
it is passed to the cooling bed. 

Inspection of Carnegie Schoen Wheels is very rigid. When cold, the 
wheel is rolled to the inspection platform for its initial inspection. This 
inspection covers surface defects, location of the hub, rotundity of tread, 
and the size, which is measured in Carnegie Standard tape sizes. These 





CIRCULAR SHAPES 


505 



A. The Blank. 



B. Blank after First Forging. 




D. Wheel, after Punching, Rolling and Coning. 


Sketches Illustrating the Manufacture of Car Wheels by the Carnegie-Schoen Method. 





















506 


THE ROLLING OF STEEL 


tapes are graduated in eighth’s of an inch, beginning with seven feet for a 
zero mark. The surface defects consist principally of over-fills, under-fills, 
slivers, scale pits, and block marks, and as they are seldom deep, they may 
be removed by machining. The tape size and all defects are plainly marked 
on each wheel, the former with a stencil, the latter in chalk. After this 
preliminary inspection, the wheels are machined as required to meet the 
specifications or remove the defects. On rolled to finish wheels, the machin¬ 
ing consists of rough boring and facing of the hub and cutting in the limit 
of wear circle on the outside of the rim. The wheels are then rolled back 
to the platforms for final inspection, which is even more rigid than the first. 
In this inspection the wheels are tested for size, eccentricity and size of 
bore, position and size of hub, thickness and height of flange, radius of 
throat, thickness of rim, coning, rotundity, and soundness. After being 
re-stenciled with tape size and marks requested by the customer, such wheels 
as come within the allowable tolerances are mated and sent to the shipping 
platform. 

Heat Treating Car Wheels: Heat treating is a recent innovation in 
the manufacture of car wheels, and may be said to be still in the experi¬ 
mental stage. Owing to the irregular section of the wheel, quenching is a 
difficult process, because, if the entire wheel is quenched, the uneven cooling 
of the heavy and light parts set up stresses in the shape that result in the 
destruction of the wheel. In order to overcome this tendency, the Carnegie 
Steel Company’s research department has developed a method whereby the 
rim only is quenched, after which the w T heel, before the hub and web have 
cooled, is given a drawback at a suitable temperature under the lower 
critical range. If the hub and web are cooled in air after the quenching of 
the rim, the wheels show a dangerous tendency to crack by this method, also, 
hence the quick draw back. From an economical point of view, it would 
appear that the cheapest plan would be to quench the wheel on the rolling 
heat, but on account of unavoidable variations in the finishing temperature 
this treatment was found to be unsatisfactory. The wheels, therefore, are 
allowed to become cold after rolling and coning, when they are reheated 
above their critical range before quenching. This process is accomplished 
in a rectangular tank provided with rollers grooved to conform to the 
tread and flange and so placed in the tank that they support the wheel 
in a vertical position transverse to the tank, which contains enough of the 
quenching fluid to cover the rim only. With the rollers, which are mounted 
on a shaft connected to a motor, revolving, the wheel, at the proper tem¬ 
perature, is placed in position on the rollers, which immediately start the 
wheel revolving, or spinning, also. The spinning is continued until the rim 
becomes sufficiently cooled when it is withdrawn and immediately given a 
draw back, as stated above. The process adds considerable to the cost of 
the wheel, and though there are many wheels in service thus treated, and 
apparently with promising results, sufficient time has not yet elapsed to 
determine just to what extent the wheels are improved by the treatment. 



CIRCULAR SHAPES 


507 


The Forging of Circular Shapes: As previously indicated, only those 
circular shapes which are more than thirty inches in diameter can be 
finished by rolling on the Schoen mill. However, this plant, which 
represents the circular shape department of the Homestead works, produces 
a great number of smaller circular shapes by forging only. These smaller 
shapes include such articles as wheels for low type street cars; double 
flanged crane track wheels; automobile fly wheels; turbine discs; shaft 
couplings; pipe flanges; pistons for locomotives; gear rings; and gear blanks 
for automobiles, farm tractors, turbo generators, street cars, etc. In addi¬ 
tion to these, a miscellaneous lot of circular shapes ranging in form from 
the most intricate sections to plain discs, and in sizes from twenty-five 
pounds to five himdred and even a thousand pounds are produced. For 
forming all these shapes the same powerful presses are employed as are 
used in preparing the rolled wheel blanks, and in general the methods of 
forging are similar, with the exception that additional precautions in the 
removal of scale before forging are observed. In this connection it should 
be noted that forging will not produce the smooth finish obtained by rolling 
on the Schoen mill, and all forged articles requiring a perfectly smooth 
surface must be machined to finish. 






508 


FORGING OF AXLES , SHAFTS, ETC. 


CHAPTER XI. 

FORGING OF AXLES, SHAFTS AND OTHER ROUND SHAPES. 

SECTION I. 

HOWARD AXLE WORKS AS AN EXAMPLE OF A FORGING SHOP. 

The Plant and Its Equipment: Aside from the forging of armor 
plate and other articles required by our government, small wheels and a 
miscellaneous lot of shapes for its own use, the Carnegie Steel Company has 
restricted its market activity in the forging line to the manufacture of 
axles, shafts and similar heavy products. For these products the company 
operates a plant especially designed for the work, known as the Howard 
Axle Works, which may be taken here as an example of a modern forging 
plant. The essential equipment of the plant includes three continuous coal 
fired furnaces for heating the blooms, a twenty-four inch roughing mill of 
two stands of rolls in tandem, ten 7000 pound and two 7500 pound double 
acting steam forging hammers, three gag press straighteners, thirty double 
cutting-off and centering machines, twenty-seven rough turning lathes, two 
finishing lathes, one boring lathe, two hollow drill machines, and a complete 
heat treating plant that will be described more in detail later. The forging 
limits of the plant as to size are as follows: Maximum weight, 2500 pounds; 
maximum length, ten feet; maximum diameter, twelve inches; minimum 
diameter, three inches. As to arrangement, the layout of the plant provides 
for the most economical handling of the materials. The blooms start in 
at one end of the plant and continue in one direction, progressing step by 
step through the various operations, until, upon arrival at the other end of 
the plant, they are in a form ready for shipment. 

Precautions to be Observed in the Manufacture of Axles: As the 

failure of an axle in service usually results with serious consequences, great 
responsibility rests upon the manufacturer at all times to see that each 
and every axle is as nearly perfect as it is possible to make it. Before 
describing the processes of manufacture, it may be well to point out 
some of the things that may cause axles to fail, because the thing aimed 
at in developing a method of manufacture is the elimination of as many 
of the causes of failure as possible. There are many of these causes of 
failure, according to some writers upon the subject, but the majority may 
be traced to the following, which are to be looked upon as the chief sources 
of danger: 1. Pipe; 2. Segregation; 3. Unequal or improper heating; 
4. Slag inclusions; 5. Forging strains; 6. Incipient cracks. From this 
list it is seen at a glance that some of these sources of danger are very 




INSPECTING AND HEATING BLOOMS 


509 


difficult to eliminate and that the making of a good axle must begin with 
the making of the steel, itself. The other defects may be overcome by 
proper attention to details during the processes of rolling and forging the 
steel. Starting with the steel after it has been rolled into blooms, which 
must correspond in dimensions and weight to the size of the axles it is 
intended for, the various steps in the process of manufacture at these works 
are as follows: 

Inspection of the Blooms: Located at Homestead, Pa., the Howard 
Works receives its steel from the Homestead Steel Works at Munhall. 
Here, before the steel is shipped to the axle works, the blooms are subjected 
to a rigid inspection. Those blooms that show any signs of pipe or 
insufficient discard at the blooming mill shears are rejected. Surface 
defects, such as seams, slivers and surface cracks, are carefully chipped 
out, and those blooms in which the defects extend beyond certain depths, 
or occur on the part that corresponds to the wheel seat are also discarded. 
Such blooms as pass the inspection are shipped to the axle works, where 
they are stored under cover until needed. 

Heating the Blooms: The proper heating of the blooms for forging 
requires that they be uniformly heated throughout and be brought grad¬ 
ually to the forging temperature, which should be kept as low as possible 
and yet permit the work to be done. The advantages of a low finishing 
temperature in securing maximum grain refinement is readily understood. 
The importance of heating slowly is also realized, when it is pointed out 
that rapid heating may cause the outside of the bloom, which is first to 
rise in temperature, to expand away from the more slowly heating core and 
thus cause ruptures that may not be welded up by the action of the hammers. 
Slow heating gives the heat a chance to “soak” into the bloom, thus giving 
that uniformity in temperature from center to surface so necessary to secure 
a finished forging of the best quality. - As to the proper temperature, the 
manufacturer has always had to depend upon the eye and judgment of the 
trained heater in the past, and must continue to do so to a great extent in 
the future. The use of pyrometers does not replace this human element, 
because the pyrometer records the temperature of the furnace and not of 
the steel, particularly in the case of the continuous furnace. The rate of 
heating is fixed by the type of furnace. At these works, therefore, the 
continuous furnace is used because this type heats up the steel very grad¬ 
ually. The bloom is placed in the furnace at the cold end and is slowly 
pushed toward the hot end, so that it reaches a full forging temperature 
only a short time before it is drawn from the furnace. 

The Rolling and Forging Operation: Having been brought to the 
proper temperature for forging, the blooms, within a certain range of sizes, 
are pushed out of the hot end of the heating furnaces upon a conveyor, 
which serves all three furnaces, and are carried by it to the rolling mill. 





510 


FORGING OF AXLES, SHAFTS, ETC. 


This mill consists of two stands of rolls in tandem, as previously stated. 
Each stand is provided with four passes cut to take four different sizes of 
square blooms. These sizes are 63^, 7^, 8 and 83^ inches. The passes 
are shaped to round off the corners of the bloom, to secure which result 
is the main object in the use of the mill. The reduction in cross sectional 
area due to the rolling varies from 33^% to 5%. From the mill, a roll 
table distributes the blooms to the hammers, which are arranged in two 
rows, one on each side of the table. Adjustable deflecting rails built in 
the side guards of the table serve to divert the blooms to small receiving 
tables, of which there is one for each hammer, and leave them in positions 
to be most conveniently grasped by the hammer tongs, which are suspended 
from cranes. The tongs having been quickly clamped on, the bloom is 
swung around between the forming dies of the hammer. These dies are 
provided, when desired, with two or more grooves; one, the plain groove 
used to do the greater part of the forging, is located directly under the 
piston rod, while the other grooves, used to form special sections, such as 
the journals, are placed beside the plain groove. The forging is begun at 
the middle of the bloom, which is rapidly reduced by heavy blows of the 
hammer, the forging progressing toward the free end of the bloom. Here, 
by the special grooves in the die, the journal or other special section is 
formed by a few strokes, when the piece is again placed in the plain groove, 
and the forging is smoothed up and brought, by light strokes of the hammer, 
to correct diameter, which is determined by caliper. The tup is then 
brought to rest upon the axle, which is held between the dies while the 
tongs are released, and those on the opposite side of the hammer are made 
fast to the finished end. The other end of the axle is then forged down 
like the first, except that, in addition to diameter, the length is also fixed. 
The crane is then swung around, and the axle is placed on the cooling bed, 
where it is supported about three feet above the floor by two rails, which 
arrangement allows it to be cooled uniformly by the air. The average 
reduction in cross sectional area under the hammer is about 50%. Forgings 
requiring blooms larger than eight and one-half inches are reduced entirely 
by hammer. Two crews, each made up of a hammerman, who has charge 
of the forging, and three helpers, and one hammer driver, are assigned to 
each hammer. The crews work alternately, each crew completing one axle 
at a time. 

Advantages of the Method: Aside from the increased tonnage made 
possible by the rapidity of the work, the method of forging employed at 
Howard presents many advantages which bear directly upon the quality 
of the product. The rolling mill, which accomplishes only a small fraction 
of the total work done upon the axle, is a great help to the hammers. By 
rounding off the corners of the bloom, it practically eliminates all danger 
of forming hammer laps, and permits the forging to be accomplished in the 
shortest time possible. Hence a low initial temperature can be used for 
forging, and the work can be completed at a more uniform temperature. 




FINISHING PROCESSES 


511 


This uniformity of the finishing temperature is a very noticeable feature 
at Howard. Thus, in observing closely various axles at different stages 
of the forging operation the eye can detect little difference in temperature 
between those axles on which the forging has just begun and those that 
are being finished. That this rapid method of forging on one heat is far 
superior to the old method of forging on two heats is apparent, because 
it not only promotes greater uniformity in individual axles but eliminates, 
to a far greater degree, the variation in different axles. 


SECTION II. 

FINISHING PROCESSES FOR FORGINGS. 

Straightening: Except in the case of heat treated axles, and driving 
and trailing axles, the next step after the forging is the straightening, which 
is accomplished by means of gag presses. From the cooling beds the 
forgings are carried forward by over-head cranes to similar beds in front 
of the presses. Here each axle is inspected for straightness, and those 
that require it are straightened. Heat treated axles are straightened after 
being treated, but driving and trailing axles are too large to be straightened 
by the gag press. 

Cutting=off and Centering: After passing the inspection for straight¬ 
ness, the forgings are moved forward by overhead cranes and distributed 
to the cutting-off lathes. These lathes are double combination cutting-off 
and centering machines, and are designed to work on both ends of the forging 
at the same time. Upon being inserted in this machine, the forging is 
grasped at the wheel seats by adjustable revolving centering clamps, which 

hold it firmly to the central axis of ro¬ 
tation, while two cutting tools, placed 
one at each end and adjusted to the 
correct length, are brought to bear 
and cut off the excess metal at the 
ends. In this cutting, a tolerance of 
one-eighth inch over length and noth¬ 
ing under is permitted. When these 
tools have cut to within about one- 
half inch of the center, they are run 
back out of the way, the pieces of ex¬ 
cess metal are detached with a sledge, 
and with the forging still held by 
the centering clamps, the revolving 
centering tools are brought to bear 
at each end. These tools are shaped 
to cut a 60 degree cone-shaped cen¬ 
tering hole, five-eighths inch in depth, 
one and one-eighth inch in diameter at the top, and with a clearance hole 


60 c 




r 


1 7 



Fig. 102. Carnegie Standard Centerin; 
for Axles. 










512 


FORGING OF AXLES, SHAFTS, ETC. 


for points at the bottom one-half inch in depth and three-eighths inch in 
diameter. When axles are ordered to be smooth forged only, the operation 
of cutting off and centering completes the work done by the mill. On such 
axles some excess stock is necessarily left on those parts that are to be 
finished later. This allowance on car axles is generally one-half to three- 
fourths inch over the finished diameters of the end collars, journals, and 
dust guards, and one-fourth to three-eighths inch on wheelseats. 

Rough Turning: On account of the saving that can be effected in 
handling and transportation of excess weight, it is a decided advantage to 
both the customer and the shop, especially to the latter, that all rough 
turning be done before shipment is made, as it is only by rough turning 
that certain flaws can be detected. Rough turned material falls into two 
classes, known as “rough turned on journals and wheelseats,” and “rough 
turned all over.” Axles of the first class are put into service with the 
center portions between the wheelseats smooth forged to size. In the 
case of axles rough turned all over, the center portions are forged slightly 
over size to provide for the metal removed in turning to size. In the case 
of car axles or other axles with a tapered body, this metal is removed at 
the same time (or after) the journals and wheelseats are rough turned, 
in a special lathe provided with two tools controlled by a former-bar whose 
contour is the same as the middle portion of the axle. In finishing rough 
turned axles, the wheelseats are finish-turned only, while the dust guards, 
journals and collars are finish-turned and burnished, and in order to provide 
the excess metal required for this work, these parts are rough turned one- 
eighth inch over size on their diameters. 

Hollow Boring: Owing to the many apparent advantages arising 
therefrom, the practice of boring large axles and forgings longitudinally 
through the center is being advocated more and more strongly. These 
advantages are briefly discussed imder the following headings: 

1. Piping, it will be recalled, was given as one of the causes of failure. 
While the Carnegie Steel Company, by a generous discard and close 
inspection, aims to eliminate this defect, yet it is possible that some forms 
of piping, notably compound pipes, may escape both the discard and the 
inspection, and remain in the axle as a menace to safety. Hollow boring 
gives the inspectors a chance to detect this hidden pipe. 

2. Segregation was given as another source of failure. This defect 
cannot be entirely overcome in the manufacture of steel, and inspection is 
no safeguard against it. But as the area of greatest segregation lies about 
the central axis, boring a hole of proper size longitudinally through the 
center should, and does, remove the greater part of all the segregated 
material from the axle. 

3. Strength and Weight: The central portion of an axle removed 
by boring is really a non-essential part so far as strength is concerned. 



HEAT TREATING FORGINGS 


513 


The transverse strength of rounds is proportional to the cubes of their 
diameters. So, for example, if a three inch bore be made in a six inch axle, 
the maximum loss in strength is but 12.5%; in an eight inch axle, but 5.25%. 
These figures represent the loss in strength provided the center is as strong 
asthe outerportion, which condition is never true in axles or similar forgings, 
so that the actual loss in strength in nearly every case would be much less 
than these figures indicate. Again, the axle with the bored center may 
actually be stronger than it would have been solid, provided it contained 
much segregated material or the remnant of a pipe—conditions that favor 
the formation of internal cracks. Another factor concerns the relation 
between the loss in strength and the loss in weight. In this connection 
it will be observed that, whereas the strength varies as the cube of the 
diameters, the weight varies as the squares. Referring to the example just 
cited, and applying this law, the reader will find that while in the case 
of the six and eight inch axles, the three inch boring gives a loss in strength 
of 12.5% and 5.25%, respectively, the loss in weight is 25% for the first 
and 14.3% for the second. 

4. Hollow Boring and Heat Treating: As an aid in heat treating, 
especially in quenching and tempering, or toughening, hollow boring is of 
great importance. In heating, it permits the heat to be absorbed much 
more rapidly, and in quenching, the heat is more rapidly removed than 
in solid pieces, with the result that the structure is more uniform. Further¬ 
more, contraction and expansion strains are largely overcome, and shrinkage 
cavities in the center are avoided. The American Society for Testing 
Materials specify that all forgings over seven inches in diameter that are 
to be quenched shall be bored. The diameter of the hole bored should 
equal or exceed 20% of the largest diameter of the forging exclusive of 
collars or flanges. Howard Axle Works are equipped to bore holes either 
two or three inches in diameter. 

The Heat Treating Plant is housed in the same building with the 
hammers and lathes and consists of two furnaces for heating with the 
forgings in a horizontal position, one furnace for heating the material in 
a vertical position, one water quenching tank, one oil quenching tank, and 
all the necessary supplemental equipment for handling and testing the 
material. 

The Furnaces: The inside working space of the two furnaces of the 
first type are each twenty-four feet in length and nine feet in width, and are 
designed to heat uniformly to a height of about four feet above the bottom. 
They are provided with removable bottoms of the car type, which much 
facilitates the charging and drawing operations. This bottom is moved 
into and out of the furnace by means of a toothed rack attached to the 
bottom of the car and a stationary pinion actuated by an electric motor, the 
car itself resting on rollers that move over a double track. The doors of the 
furnace are of the vertically lifting type, and are hydraulically operated. 






514 


FORGING OF AXLES , SHAFTS , ETC. 


These features, together with the close proximity of the quenching tanks, 
permit the drawing and quenching of a charge in the quickest possible time, 
less than a minute being required to transfer a charge from the closed furnace 
to either of the quenching tanks. The measures taken to secure uniform 
heating are particularly noticeable in this furnace. The furnace is of the 
reversing flame type, in which natural gas is employed as fuel, and is heated 
by means of burners placed at space intervals of less than two feet along 
each side, thus permitting the temperature at any point in the furnace to 
be controlled to a nicety. At the top, the furnace is closed with a roof, 
arched from side to side, while, inside, high bridge walls extend along in 
front of the gas burners to prevent the flames from impinging upon the 
charge. In order that the entire surface of the material may be exposed 
to heat of the same intensity, the charge is supported at a height of about 
eighteen inches above the floor of the car bottom by two steel rails that 
extend the entire length of the car. These rails are spaced about four feet 
apart and are supported by castings in the form of four-legged stools. The 
floor of the car bottom is constructed of brick laid upon a bottom of steel 
plates, and is of such thickness as to give ample insulation from the heat of 
the furnace. The bottom is made to fit the furnace neatly, and the escape 
of hot gases from the heating chamber is prevented by means of sand seals. 
The construction of the furnace for heating the charge in a vertical position 
is somewhat like that of a soaking pit. It has a capacity of about six axles 
and sufficient head room for maximum lengths of ten feet. In operating 
this type of furnace, the axles are loaded on a cast steel rack, which is 
specially designed to support them in a vertical position, and are lowered 
through the top into the furnace where they are maintained in a vertical 
position throughout the heating operation. This furnace is seldom used, 
as more satisfactory operating conditions are obtained by using the other 
type. For taking temperatures the Siemens Water pyrometer is used 
exclusively. 

The Quenching Tanks: For use in connection with these heating 
furnaces, the plant is equipped with one water quenching and one oil quench¬ 
ing tank. These tanks are both placed as near as possible to the furnaces, 
the water tank being directly in front of one of the furnaces of the horizontal¬ 
heating type. This tank, approximately twenty-five feet long, twelve feet 
wide and fourteen feet deep, is of the sub level type and is constructed of 
concrete. When in use, the water level lies about two feet above the floor 
of the shop. So, an ample volume of water is supplied for any charge it is 
practicable to handle, and, in addition, provision is made whereby fresh 
water may be introduced during the quenching operation at one corner of 
the tank and the excess conducted away at the diagonally opposite corner, 
both inlet and outlet being located near the top of the tank. Two beams 
extending the full length of the tank and supported about two feet above 
the bottom, prevent the charge from resting on the bottom when lowered 
by the crane, thus securing more uniform cooling. The oil quenching tank 





HEAT TREATING FORGINGS 


515 


is some sixteen feet in length, nine feet in width, and ten feet in depth, 
inside. It is made in two parts—an oil container and a cooling jacket. 
The container is made of steel plates and is set within the cooler, which is 
constructed of concrete and is about twenty inches longer and wider than 
the container, so that a space of about ten inches separates the walls of 
the two vessels. This space is kept filled with cold water, which serves 
to prevent the temperature of the oil rising too high during quenching, and 
to cool it down rapidly after each charge. 

The Testing Equipment includes all the latest devices for testing 
materials. In the shop, two hollow drill machines for cutting out tests are 
provided, and as all heat treated axles are given individual shock tests, 
a drop testing machine for giving these proof tests is also located here. 
Two drop testing machines, adapted for testing axles in accordance with 
standard specifications are provided. Other physical tests are made in the 
physical laboratory, which is equipped with one planing, one turning, one 
pulling, one torsional, one bending and one Brinell machine, and all the 
supplemental appliances for accurate testing. 

Advantages of Heat Treating Axles: While the proper heat treating 
of axles is accomplished with some difficulty on account of their size, and 
is attended with great danger if improperly done, yet with proper equip¬ 
ment, great care and good judgment, born of knowledge and experience on 
the part of the operator, the dangers may be eliminated, and decided 
advantages result therefrom. It is the only way in which the grain struc¬ 
ture can be refined and made uniform, and in doing this all the evils due 
to variations in the grain, which result from the heating and working of 
the bloom, are overcome, as well as forging strains. But greatest of all 
these advantages is the improvement in mechanical properties effected 
through correct heat treatment. It offers the only positive means of 
markedly increasing the strength and wearing properties of axles without 
in any way increasing their weight—a thing that is much desired under 
modern conditions of traffic. 





516 


CONSTITUTION OF STEEL 


PART III. 

THE CONSTITUTION HEAT TREATMENT AND COMPOSITION 

OF STEEL. 

Introductory: It is the desire in this part of this little book to center 
the interest of the reader chiefly about the heat treatment of steel. So 
much progress in the study of this subject has been made in recent years 
that many are inclined to look upon it as something new. That remarkable 
changes in the^hysical properties of a given steel can be brought about 
through the agency of heat alone has been known for many years, but 
until 1890 the subject had received very little attention from scientists. 
Up to that time both the scientific knowledge about the subject and the 
technical application of the art of heat treatment were very limited, being 
confined for the most part to the making of tools and a few specialties. 
The invention of the automobile, the aeroplane, and other machines, the 
different parts of which are required to be light and at the same time suit¬ 
able for the usages to which the parts are subjected, gave rise to demands 
for steel of great strength combined with various other specific properties. 
These demands directed the attention of investigators to heat treatment 
because it was found that this was the only means of meeting these require¬ 
ments. Practically all alloy steels must be heat treated in some way, and 
few steels in their natural state will give their full value in service, so that 
the various combinations of static and dynamic strength and wearing 
qualities required can be obtained in their highest degree only by adjusting 
and correlating both the chemical composition and the heat treatment. 
Just as certain chemical components intensify one set of properties, and 
others another set, so the heat treatment may be changed to develop 
different qualities in a similar way. Thus, by combining the proper chemical 
composition with the proper heat treatment, there results a product posses¬ 
sing in the highest degree the properties most desired for the work the 
steel is to do. So it is evident that the intelligent application of heat 
treatment to secure the best results requires a thorough knowledge, on the 
part of those supervising the work, of the composition of the steel and the 
effect of the various elements that are to be found in all steels or that may 
be added as alloys to produce the special steels. Again: Heat treatment 
consists in heating and cooling steel under conditions that will produce 
the desired change or changes in physical properties, and embraces the 
three processes of annealing, hardening, and tempering, to which may be 





CONSTITUTION OF STEEL 


517 


added the special processes known as “process annealing/' “patenting," 
“case hardening," etc. The remarkable changes in properties that may 
be obtained, together with the phenomena observed during heating and 
cooling, all connote vital changes that are brought about by the heat 
treatment. As no change in composition of the metal takes place, the 
cause for the phenomena must be sought in changes of arrangement or 
condition of the constituents of the steel itself. Another pre-requisite, 
then, to the study of heat treatment is the study of the structure and con¬ 
stituents of steel, a thorough knowledge of which is essential to any 
understanding of the subject, whatever. For this reason, the study of heat 
treatment should be prefaced by a brief summary of the knowledge con¬ 
cerning the structure and constitution of steel. 

Before beginning this study, however, the student should understand 
that part III of this book is intended merely as an introduction to the study 
of metallography, heat treatment and composition of steel. Those who 
desire a further knowledge of these valuable and fascinating subjects are 
referred to such authorities as Albert Sauveur 1 , whose plan of developing 
the subject is closely followed in this study; H. M. Howe 2 , whose iron 
carbon diagrams are used herein; and D. K. Bullens 3 , whose practices in 
heat treatment are frequently referred to. 


iSee the Metallography and Heat Treatment of Iron and Steel, Published by 
Sauveur and Boylston, Metallurgical Engineers, Cambridge, Mass. 

2See Iron, Steel and Other Alloys, and The Metallography of Iron and Steel. 
Both published by McGraw-Hill Book Company, Inc., 239 West 39th Street, New 
York. 

sSee Steel and Its Heat Treatment, Published by John Wiley & Sons, Inc.. 
New York City. _ i 


f 





518 


CONSTITUENTS OF STEEL 


CHAPTER I. 

THE CONSTITUTION AND STRUCTURE OF PLAIN STEEL. 

SECTION I. 

' i ’• • » "» ' ' . V r 

STEEL AS AN ALLOY OF IRON AND CARBON. 

The Constituents of Steel: Steel is not a single element or compound, 
but a complex artificial product, composed of many elements held in the 
solid mass as a mechanical mixture of alloys and chemical compounds with 
the element iron. In ordinary steel, these elements are iron, carbon, 
manganese, phosphorus, sulphur, silicon and oxygen, with traces of nitrogen, 
hydrogen and other elements, such as aluminum, copper and arsenic. Of 
these, all are to be considered as impurities except carbon, which is an 
essential ingredient, and manganese, or other elements added for a definite 
purpose. For the sake of simplicity and brevity only pure steel, consisting 
of the two essential elements, iron and carbon, will be considered in this 
chapter. Even in this case steel is found to be an aggregate made up of 
mineral-like components, some of which are visible only with the aid of 
the microscope after the surface of the specimen has been highly polished 
and etched with dilute acids or other corrosive mixtures which affect the 
various constituents in different ways. To the structure thus revealed by 
the microscope the term micro-structure is given, to distinguish it from the 
macroscopic structures, or those visible to the naked eye; and to the 
different constituents mineralogical names have been applied. Thus, in 
pure steels which have cooled slowly from a high temperature, three dis¬ 
tinct constituents are recognized. They are called ferrite, pearlite, and 
cementite, and in the different steels will vary in amount according to the 
carbon content. 

Ferrite is the term applied to pure iron, i. e., carbonless iron, when 
it is considered as a microstructural constituent of steel. It is soft, ductile 
and relatively weak, having a tensile strength of about 40,000 pounds 
and an elongation of 40 per cent, in two inches. It has practically no 
hardening power, a high electric conductivity, and can be magnetized. 
It appears white in color after being etched with dilute alcoholic nitric or 
picric acids. It is best seen in slowly cooled steels in which the carbon 
content is less than .50%. In such steels it appears as a network surround¬ 
ing bodies of pearlite, another constituent of steel to be described shortly. 

Cementite: As already stated, iron and carbon are the essential 
elements in steel, and of these carbon may be termed the controlling element. 
When steels are cooled slowly from high temperatures, from the molten 




THE CONSTITUTION OF STEEL 


519 


1. Photomicrograph 
showing a grain of pear- 
lite surrounded with free 
ferrite as a net work. 
Specimentakenfrom an¬ 
nealed steel containing 
carbon .48 per cent, and 
manganese .54 per cent. 
Magnified 750 diameters 

Etched first in 5% 
alcoholic picric acid for 
eight seconds, then in 
5% alcoholic nitric acid 
for five seconds. White 
area represents ferrite. 
On account of a too rapid 
rate of cooling, the pearl - 
lite is not fully devel¬ 
oped. Compare with 
Figs. 48 and 113. 



2. Photomicrograph 
of a specimen of steel 
containing carbon to the 
extent of 1.50 percent. 
The excess cementite is 
here seen in the form of 
spines, or needles. 

Magnified 100 diam¬ 
eters. Etched for eight 
seconds in five percent, 
alcoholic picric acid and 
for two seconds in five 
per cent, nitric acid, 
making the free cement¬ 
ite, which stands in 
relief, brilliant white 
in color. 



Fig. 103. Photomicrographs illustrating the micro structure of Steel. 
(Photographs prepared by O. M. Ash. Portland office, U. S. Steel Products Co.) 








520 


CONSTITUTION OF STEEL 


state, for example, all the carbon is found combined with a definite amount 
of iron in the form of a carbide of iron corresponding to the chemical formula 
FesC. This compound consists of carbon, 6.67 per cent, and iron, 93.33 
per cent., and it is known micrographically as cementite. Any excess iron 
is practically free of carbon at atmospheric temperatures and remains as 
ferrite in steels that have cooled slowly. Little is known about the 
properties of cementite except that it is very hard and brittle. Indeed, 
it is the hardest component of steel, and will scratch glass and feldspar 
but not quartz. It is about two-thirds as magnetic as pure iron under an 
exciting current. After polishing the surface of steel, it stands in relief, 
and is brilliant white after etching with dilute hydrochloric or picric acids. 
It occurs free in ordinary steels of more than .90% carbon, in which it ; 
appears as a network or as spines and needles. It takes its name from 
cement steel, made by the cementation process, which contains a great 
deal of this carbide, FeaC. 

Pearlite: One of the most remarkable characteristics of cementite 
and ferrite is their power of forming the conglomerate known as pearlite. 
During the process of slowly cooling steel from higher temperatures, say 
above 1000° C., it has been found that cementite and ferrite are liberated 
and form, at about 700° C., a mechanical mixture made up of definite amounts 
of each and in the proportion of about seven parts ferrite to one part 
cementite, so that the resultant conglomerate will contain approximately 
.90% carbon. This constituent then consists of interstratified layers or bands 
of ferrite and cementite, and is called pearlite on account of its resemblance 
to mother of pearl. While pearlite commonly occurs in slowly cooled steels 
in the lamellar formation, composed of alternate layers of ferrite and 
cementite, it may under different rates of cooling and dependent on the 
relative amounts of ferrite and cementite present, exist in other formations, 
or phases, of which some authorities have recognized at least four, making 
in all five modifications. Normal pearlite has a maximum tensile strength 
of about 105,000 pounds, and an elongation of about 10% in two inches. It is 
regarded as a separate and distinct constituent of steel because it forms 
distinct masses or “grains,” always contains this definite percentage of 
carbon and is always formed at a definite temperature, or a range of 
temperatures, to be more exact. 

Manner of Freezing of Solutions and Alloys: In order to clarify 

the explanation of the formation of pearlite, it is necessary to digress to 
the extent of explaining some of the freezing laws of solutions. A study 
of the freezing of solutions has shown that they fall into two classes, namely, 
those in which the ingredients in solution in the liquid state remain in 
solution in the solid state and those in which the state of solution is not 
maintained in the solid state, that is, those in which the ingredients separate 
on freezing. 

An Example of the First Class of Solutions: One of the best examples 
of the first kind of solution is a mixture of gold and silver. If quantities of 


t 














FREEZING OF ALLOYS 


521 


these two metals be placed in a vessel and heated until they melt, a homo¬ 
geneous mixture, or a liquid solution, results; and if this mixture be allowed 
to cool to the solid state, it is still homogeneous, that is, it is a solid solution. 
A study of many mixtures in which the proportions of gold to silver are varied 
shows that freezing begins at a different temperature for each mixture. 
Pure gold freezes at 1062° C. and pure silver at 961° C., and the freezing 
points of the mixtures occur between these two points. Unlike the pure metals, 
however, these mixtures do not solidifycompletely at a constant temperature, 
but their freezing is prolonged through ranges of temperature. These facts, 
definitely determined by experiment, may be represented by a diagram, or 
curve, such as the following, in which the ordinates represent temperatures 
and the abscissae the percentage of gold or silver or both. 



Fig. 104. Diagram of the Freezing of Liquid Gold-Silver Alloys. 

To illustrate further, suppose 60 oz. of gold be mixed with 40 oz. of 
silver, and the whole heated to a temperature of 1090° C. The locus of 
this point would be at “1” in the region of the liquid state. If now this 
molten solution be allowed to cool slowly, crystallization will begin at 
“f,” about 1041° C., and end at “s,” about 990° C. Although as a matter 
of fact the first crystals formed will contain more gold than the liquid, 
the proportion being, in this case, about 90 parts gold to 10 parts silver, 
and the last more silver than the liquid, the average composition of all 
will be the, same, namely, 60% gold and 40% silver. Furthermore, while 
solidification is going on, a process of diffusion is also taking place, which 
tends to adjust the composition of each individual crystal, bringing it 
nearer that of the average. Thus, while the composition of the solid body 
as a whole varies slightly, each crystal, or any small part of the body, is 
practically homogeneous and made up of a mixture of gold and silver, so 
intimate that they are not distinguishable. 



















522 


THE CONSTITUTION OF STEEL 


Example of the Second Class of Solutions—Salt and Water: It is 

a well known fact that a solution of common table salt freezes at a lower 
temperature than pure water. This lowering of the freezing point, or rather 
the temperature at which freezing begins, varies with the proportion of 
salt to water until this proportion has reached the definite limit of 23.5%, 
when any further addition of salt causes the point at which freezing begins to 
rise. This lowest temperature, at which the solution containing 23.5% of salt 
freezes, is —22° C. These facts are represented by the diagram of Fig. 105. 

Two or three examples 
will suffice to explain the 
freezing of solutions contain¬ 
ing varying amounts of salt, 
and any other points about 
the diagram that may not be 
clear. Thus, suppose a solu¬ 
tion containing 10% of salt is 
at a temperature indicated by 
‘T'\ Although water freezes 
at 0° C., the temperature of 
this solution must fall to the 

% Water 100 90 80 76.5 70 60 noint “f ” about —10° C 

% Salt o 10 20 23.5 30 4Q point r » aDOUt 1 U 

Fig. 105. Diagram Representing the Freezing before freezing begins. Here, 
of Solutions of Salt in Water. unlike the solution of gold 

and silver, crystals of pure water begin to separate from the solution. The 
separation of these crystals has the effect of increasing the percentage of salt 
in the mother liquor, so that the separation of the water crystals continues 
only so long as the temperature is being lowered. Furthermore, if the rate 
of cooling has been uniform down to the point “f,” a marked retardation 
takes place here, because the heat of fusion of the water must be removed 
before ice can be formed. With the removal of this heat, however, and that 
necessary to lower the temperature of the remaining solution, the separa¬ 
tion of ice crystals continues, causing a concentration of salt in the mother 
liquor that bears a definite relation to the temperature as indicated by the 
line M O. Finally, when a temperature of —22° C. is reached, the mother 
liquor, which now contains 23.5% of salt, freezes as rapidly as the heat of 
fusion is abstracted. When all this liquor has solidified, the temperature 
of the solid mass will continue to fall uniformly in a manner similar to that 
before freezing began. 

If instead of the weak solution, a strong brine containing more than 
23.5% of salt is substituted in the experiment just described, it is found 
that, just as ice separated along the line M O., salt crystals separate out 
along the line N Oifntil the temperature —22° C. is reached and the mother 
liquor contains 23.5% of salt. This liquor then freezes as described before. 
When these facts were first observed, it was thought that the mother liquor 
that is the last to freeze was a hydrate of sodium chloride of the formula 
NaCl.lOH^O. and was called, therefore, the cryohydrate, cold hydrate, 
meaning a hydrate that could exist in the solid state only at low temper- 















FREEZING OF ALLOYS 


523 


atures. It has since been shown that these cryohydrates are not chemical 
compounds, though they have a definite composition, but are mechanical 
mixtures made up of crystallized salt and ice in intimate contact. 

Lead and Tin Solutions as Another Example of the Second Kind 
of Freezing: Many of the fused alloys exhibit the same phenomena in 
freezing that saline solutions do, showing that their constituent metals 
form a solution when in the liquid state but that they are insoluble in one 
another in the solid state. As an example of such an alloy, that of lead 
and tin is most convenient for study. To cite a specific example, let a 
mixture composed of 30% tin and 70% lead be heated to a temperature 
of 350° C. As this temperature is above the fusion points of both lead and 
tin, which melt at 327° C. and 232° C., respectively, it is sufficiently high 
to insure that the mixture will be completely fused. Now, as this solution 
cools down, no crystallization takes place until a temperature of about 
270° C. is reached, when crystals of lead begin *to separate out, making 
the remaining solution poorer in lead but richer in tin in the same way as 
the ratio of salt to water became greater during the freezing of the weak 
saline solution. Likewise, as in the case of the salt solution, the separation 
of the lead causes a retardation of the rate of cooling, showing that heat is 
evolved thereby; and the freezing point of the mother liquor becomes lower, 
so that no further separation of lead takes place until more heat is 
abstracted. If the cooling be continued, however, the separation of the 
lead will also continue, and if proper measures be taken, a number of loci 
may be obtained of the cooling curves for alloys of different composition, 
which, when plotted, give the curve M O as represented in the diagram 
of Fig. 106. 


Freezing point 
of pure lead. 


Freezing point 
of pure tin. 


Fig. 106. Diagram Illustrating the Freezing of Lead-Tin Alloys. 

When the cooling and the accompanying separation of lead has reached 
the point O., corresponding to a temperature of 180° C. and 31% of lead, 
or 69% tin, in the mother liquor, the whole mass becomes solid, forming 
a banded structure composed of minute crystals of lead and tin and cor¬ 
responding to the cryohydrate of salt and water, but called, in the case 
of alloys, eutectic alloy, which signifies easily melted alloy. To the right 















Temperatures—Degrees Centigrade 


524 


CONSTITUTION OF STEEL 


of the point 0, tin separates along N O like lead along M O. This manner 
of freezing, where one metal separates alone, is known as selective freezing 
to distinguish it from the kind of freezing illustrated by the gold-silver 
alloys, which, since both metals separate together, is known as non=selec=» 
tive freezing. 

The Iron=Carbon Eutectic: Coming now to a consideration of the 
iron carbon alloys, the student finds that the freezing of alloys of these 
two elements presents phenomena that are like those of both the gold- 
silver and the lead-tin alloys. The freezing of these alloys is represented 
by the following diagram, from which it is seen that the carbon content 


IRON-CARBON SYSTEM 



Fig. 107. Diagram Demonstrating the Freezing and 
After H. M. Howe. 


Cooling of Iron Carbon Alloys. 


of the eutectic alloy is about 4.30%. Therefore, when alloys that contain 
more than this amount of carbon are cooled from temperatures above the 
line MON, carbon in the form of graphite separates along N O until 
the point O is reached, when the eutectic solidifies. Naturally, the reader 
would expect a similar separation of iron along the line M O; but it is 
here that the freezing of the solution produces phenomena similar to the 
freezing of gold-silver alloys, for it is found that, instead of pure iron separat- 

































































FREEZING OF IRON-CARBON ALLOYS 


525 


ing, a definite mixture, or alloy, containing approximately 2.0% carbon and 
called primary austenite, separates from all mixtures in which the carbon 
content is two per cent, or more. By drawing in the vertical line A D, 
corresponding to about 2.0% carbon, this diagram is divided into two 
parts. The part to the right of A D shows the freezing of the iron carbon 
alloys to be like that of the lead-tin alloys, that is, selective, while that 
part to the left of A D shows that the freezing of all iron-carbon alloys 
whose carbon content is less than 2.0% is non-selective and analogous to 
the freezing of the gold-silver alloy. For example, suppose an iron-carbon 
alloy containing 1.0% carbon to be at a temperature of 1500° C. It is in the 
liquid state and represents a homogeneous mixture of iron and carbon, or 
a solution of carbon or an iron-carbon compound in iron. If now this solution 
is allowed to cool, crystallization will begin when the temperature indicated 
by the corresponding point “f” on the line M O is reached, and will continue 
up to the point “s” on the line M P, when the solidification will have been 
completed. As in the case of the gold silver alloys, the first crystals 
formed are richer in iron and the last richer in carbon than the liquid, but 
diffusion takes place so that the metallic body is made up of homogeneous 
crystals containing 1.0% carbon. This solid solution is also known as 
primary austenite. Because of this difference in the freezing of the iron 
carbon alloys between those containing more than 2.0% carbon and those 
containing less than 2.0% carbon, the carbon content of 2.0% may be con¬ 
sidered as the dividing line between steel and pig iron; consequently, this 
study is concerned mainly in the changes that occur in alloys whose com¬ 
position is represented by the region in the diagram that lies to the left 
of the line A D 

Formation of Pearlite, or the Eutectoid: By studying the cooling 
of the primary austenite through the region below M P, it is found that this 
solid solution of carbon in iron imdergoes changes similar in character to those 
presented by the freezing of the liquid solution. These changes are repre¬ 
sented by a secondary set of curves as shown in the part of the diagram to the 
left of AD. This diagram indicates that a substance corresponding to the 
eutectic of liquid alloys is formed and that it contains about .90% carbon, 
but since it is formed from a solid solution, it is called the eutectoid, a 
term that means “something of the nature of an eutectic.” It will be 
observed that as the primary austenite is cooled from M P, the line of 
complete solidification, that any alloy with a carbon content greater than 
.90% precipitates iron carbide, Fe 3 C, along the line P O', whereas those, 
in which the carbon content is less than .90%, throw out of solution pure 
iron or ferrite along M' O' until the eutectoid composition is reached. 
The unchanged alloy, to which the term mother metal may be applied, 
then undergoes a change wherein the precipitation of both the iron and 
the iron carbide, Fe 3 C, is completed simultaneously, with the lesult that the 
eutectoid thus formed consists of interstratified layers offeniteandcement- 
ite, commonly called pearlite, as previously explained. Hence, the term 
eutectoid is often applied to pearlite, when it is desired to indicate the 



526 


CONSTITUTION OF STEEL 


manner of its formation and its structural characteristics. Since the metal 
is in the solid form during these changes, it having reached its freezing 
point 500° to 800° C. above the temperature of formation for pearlite, the 
cause for these changes cannot be ascribed to a change in state. While 
many theories have been advanced to explain this and other facts the 
most satisfactory explanation is that iron exists in at least two, possibly 
three, allotropic forms. Thus, below a temperature of 690° C. it exists in 
a form designated as the alpha form, in which it has no power of dissolving 
carbon or the carbide, cementite, whereas above this temperature it can 
hold this constituent in solid solution. At these higher temperatures it is 
designated as the gamma form, and the solid solution of carbon, or carbide, 
in iron, is, metallographically, called austenite. Furthermore, the change 
from austenite to pearlite is not instantaneous, and, as will be explained 
later, several transition products may intervene, the complete series being 
austenite, martensite, troostite, sorbite and pearlite. From what has been 
said, it is evident that a steel that contains .90% carbon will, if cooled 
slowly from any point above tihe critical temperature for its formation, 
consist entirely of pearlite. Such steels are designated as eutectoid steels, 
while those that contain less than .90% carbon are termed hypo=eutectoid 
steels, and those in which the carbon content exceeds .90% are called 
hyper=eutectoid steels. Other phenomena which accompany the cooling 
of the primary austenite will be described in the next section. 

Structural Composition of Slowly Cooled Steel: All steels that 
have been cooled slowly from a temperature above that for the formation 
of pearlite will contain it as a constituent. Thus, in the case of hypo- 
eutectoid steels, all the carbon present will be found as pearlitic cementite, 
the amount of pearlite being controlled by the amount of carbon present. 
Any ferrite above that required by the cementite in the formation of pearlite 
will be rejected as free, or excess, ferrite. In such steels, this excess ferrite 
is in the form of a network surrounding small masses of the pearlite. In 
the case of hyper-eutectoid steels, the amount of pearlite is again controlled 
by the carbon, but in an indirect way. As all the carbon combines with 
iron to form cementite, only a limited portion of ferrite remains for the 
formation of pearlite. As this ferrite is not sufficient to interstratify with 
all of the cementite, an excess of the latter remains. Like the rejected 
ferrite, this excess cementite will also appear as a network about the masses 
of pearlite. Thus, from the carbon content of a slowly cooled steel it is 
possible to determine accurately the structural composition, or from the 
relative proportions of pearlite and ferrite or cementite as revealed by 
the microscope, the practiced metallographer can determine the approxi¬ 
mate carbon content. 

Effect of These Constituents Upon the Physical Properties: The 

data on the physical properties of these constituents enable the student 
to imderstand the remarkable effect of carbon upon the physical properties 
of ordinary steel. In brief, the facts in their relation to the static strength 
of slowly cooled steel are as follows: 1. Each constituent has the power 

















THERMAL CRITICAL POINTS 


527 


to impart to the steel its own properties in proportion to the extent of its 
presence. 2. Ferrite has the minimum tensile strength but maximum 
ductility. 3. Pearlite has maximum tensile strength with low ductility. 
4. Cementite has great hardness and brittleness with very little strength. 
The effect of these constituents upon the properties of steel are plainly 
shown in the accompanying diagram. 


100 


S3 

03 

e-t 


c 

6 

u. 

03 

Ch 


80 40 

o 
*3 

rt 

M 

a 

_ o 


a 

03 

O 


40 £ 


20 


20 10 



Fig. 108. Diagram Showing the Approximate Influence of Carbon Upon the 
Strength and Ductility of Steel and its Relation to the Pearlite Content. 


SECTION II. 

THERMAL CRITICAL POINTS OF STEEL. 

Nature of Critical Points or Ranges of Steel: The structural and 
other changes in steel just described take place at temperatures known as 
the thermal critical points, or critical ranges, because they are points in the 
cooling or heating of the metal that are marked by the spontaneous evolution 
or absorption of heat. The most marked of these is the range commonly 
called the point of recalescence and point of decalescence. 

Thermal Critical Point for Eutectoid Steel: For example, suppose 
a piece of steel, containing .90% carbon and at a temperature of 1000° C., 
be allowed to cool slowly. If, now, the rate of cooling be carefully ascer¬ 
tained by means of a pyrometer, it will be found that the cooling proceeds 
at first at a uniformly retarded rate, thus following the law for all cooling 
bodies. But when a temperature of about 700° C. is reached, the uniformly 
retarded cooling is momentarily arrested. A pyrometer will not only fail 
to record any further decrease in temperature, but in most cases, when 
the conditions are favorable, will show that the temperature of the cooling 






528 


CONSTITUTION OF STEEL 


mass actually rises. These facts show that heat is spontaneously generated 
within the metallic body in amount sufficient to balance, or more than 
balance, that lost through radiation and conduction. If the experiment is 
performed in the dark, the steel will be observed to glow at this point due 
to the heat evolved, and so the term recalescence has been applied to it. 
Investigation has shown that the amount of heat given off in this case is 
about 16 cal. per gram of pearlite. 

Thermal Critical Points for Pure Iron: If instead of the eutectoid 
steel, a piece of the purest iron obtainable be substituted in the experiment 
just described, the cooling of this pure iron is found to be very unlike that 
of the eutectoid steel. Thus, the metal will be found to cool at a uniformly 
retarded rate till a temperature of 900° C. is reached, when a marked 
increase in retardation occurs, showing that heat is being evolved, but 
insufficient to cause an actual rise in temperature of the body of metal, 
i. e., a recalescence. The cooling will then resume a normal rate until 
the temperature of about 760° is reached, when a second evolution of heat 
takes place, but not so pronounced as in the first instance. The metal then 
cools normally to atmospheric temperatures. Thus, in pure iron there are 
two evolutions of heat, i. e., two critical points, both of which take place 
at a higher temperature than that noted for eutectoid steel and without 
actual rise in temperature. Carbonless iron, therefore, has no point of 
recalescence. 

Thermal Critical Points of Low Carbon Steel: If the same experi¬ 
ment be now performed with a steel containing even a small per cent, of 
carbon, say .10%, the influence of this element is found to be very marked. 
Three thermal retardations will be detected, the first, the most marked, 
at about 850° C., the second near 760° C., and the third at the point of 
recalescence, near 700° C. The last two are very faint. 

Thermal Critical Points of Medium Carbon Steel: If the experi¬ 
ment with low carbon steels be repeated with specimens containing higher 
and higher percentages of carbon, the upper critical points observed in the 
preceding experiment on .10% carbon steel and carbonless iron will be found 
to be lower and lower as the percentage of carbon is increased, until, finally, 
the determination of the rate of cooling of a steel containing .35% or .40% 
carbon reveals only two critical points, the upper one at about 740° C. 
and the other at the point of recalescence, 700° C. This fact means that 
the carbon has caused the two upper points observed in pure iron and low 
carbon steels to merge into one critical point. Furthermore, experiments 
on steel containing a higher per cent, of carbon than .40 show that the two 
lower critical points remaining also apparently merge into one on steels 
containing .60% carbon and over. Theoretically, this apparent merging 
should not take place till the steel is composed entirely of pearlite, that 
is, when it has the eutectoid composition and contains .85% to .90% carbon. 
The early merging is attributed to the difficulty of distinguishing by experi¬ 
ment two critical points so close together. 























THERMAL CRITICAL POINTS 


529 


The Carbon=Iron Diagram for Steels and Methods of Notation: 
These critical points or ranges are indicated graphically in the accom¬ 
panying diagram of Fig. 109, which is seen to be the same as that used in 
explaining the formation of pearlite. This diagram refers to the critical 



Fig. 109. Diagram Showing Position of the Critical Ranges and the Relation of the 
Carbon Content to that of Pearlite and Ferrite and Cementite. 


points on cooling, which occur at temperatures somewhat lower than on 
heating. All these critical ranges are denoted by the letter “A,” followed 
by either the small letter r, an abbreviation for the French word 
“refroidissement,” cooling, or the small letter c, which stands for 
“chauffage,” signifying heating. These signs, Ar and Ac, are further 
modified by the numerals 1, 2, 3, indicating the point of recalescence, the 
second, and the third points encountered on heating, respectively. Thus, 
Acl means the first critical point passed upon heating the steel, and so on. 





















530 


CONSTITUTION OF STEEL 


The Position of the Critical Ranges is affected in many ways. Atten¬ 
tion has already been called to the difference between the ranges on heating 
and cooling! In commercially pure carbon steels, Ari almost invariably 
takes place between 690° C. and 720° C. and A^ 20 to 40 degrees higher. 
It has been well established that this lagging of the point on cooling and 
the point on heating behind the true point is a case of hysteresis, often 
observed in physical phenomena. Evidence of the correctness of this 
explanation is found in the fact that the slower the heating and cooling 
the nearer the two points approach each other. The speed of cooling or 
heating, then, is the first factor affecting the position of these points. A 
second factor influencing the positions of Ar* is found in the temperature 
to which the steel is heated before cooling begins. The higher this tem¬ 
perature and the longer it is held at the high temperature the lower the 
position of Ar A will be; but this change in position of the critical point is 
not pronounced and takes place very gradually and slowly. A third factor 
is that of chemical composition. In general the presence of impurities in 
the steel have a tendency to lower the position of Ac and Ar, and in some 
cases this tendency is very decided. Thus, manganese lowers the position 
of Ar some 25° C. to 50° C. for each per cent, of that element present in the 
steel. Nickel and copper also lower the Ar range. In the case of nickel 
and manganese the lowering is so pronounced that in a steel containing 
13% Mn. or 25% Ni. no retardation is observed in cooling from a high 
to atmospheric temperature, but appears on cooling in liquid air, which 
indicates that the Ari point has been lowered in these steels to below the 
temperature of the air. In the ordinary steel of commercial quality, the 
impurities are present in so small amounts that they can cause little vari¬ 
ation in the position of the critical points. 


Changes at the Thermal Critical Points: Besides the rise in tem¬ 
perature or retardation of cooling already explained, careful investigation 
has shown that other important changes take place in steels in passing 
through these ranges. For convenience these changes and their effects 
are summed up as follows:— 

I. Changes at A 3 : The point A 3 , as already shown, applies to 
carbonless iron and steels containing less than .35% carbon. The passing 
of such steels through this point is accompanied by the following phenomena: 
1. On cooling, the metal, which above Ar 3 was contracting, undergoes a 
sudden and marked expansion in volume on passing through Ar 3 . In linear 
units the expansion amounts to about one one-thousandth of its length. This 
dilation is then immediately followed by normal contraction, again. 2 . Above 
A 3 the metal has an electrical resistance about ten times greater than its 
resistance at ordinary temperatures. At Ar 3 a sudden drop in this resist¬ 
ance takes place, after which the decrease proceeds slowly at a uniform 
rate until atmospheric temperature is reached. 3. A change in crystalline 



THERMAL CRITICAL POINTS 


531 


form of iron takes place at A 3 . Below this point iron crystallizes in the 
cubic form, but this form changes on passing AC 3 to that of the octahedra. 
4. The tensile strength of iron at the A 3 point has been shown to undergo 
a distinct discontinuity, (see page 337). 5. The dissolving power of iron for 
carbon is one of the most important changes which the properties of the metal 
undergo in passing the AC 3 point. From what has been said in the preceding 
section it may be surmised that below this point, or at least as long as 
the iron is in the alpha form, it has no power of dissolving carbon, but 
it gains this power immediately the AC 3 point has been passed. 6 . An 
abrupt structural change accompanies the passage of all low carbon steels 
through this range. It is on reaching this point that the free ferrite begins 
to be set free, which continues till the residual austenite is of the proper 
composition for the formation of pearlite. 

II. Changes at A 2 : As indicated in the iron-carbon diagram, A 2 
occurs as a separate point only in carbonless iron and in steels containing 
less than .35% carbon. Just as the retardation on cooling was found to 
be faint at this point, so the changes in properties are not so numerous 
nor so marked as at A 3 . Thus, there is no dilation, no structural change, 
no change in crystalline form, and probably no change in the dissolving 
power of iron for carbon on passing through the range A 2 . But the following 
three changes in properties on passing A 2 are to be specially noted. The 
magnetic properties undergo a marked change on passing A 2 . Above 
this point steel is non-magnetic, or para magnetic, but in passing through 
Ar 2 it suddenly becomes strongly magnetic, and gradually becomes more 
so as the cooling continues, finally gaining its full magnetism at a tem¬ 
perature of about 500° C. A distinct discontinuity in both the tensile 
strength and specific heat of iron at the A 2 point has been shown to take 
place. 

III. Changes at A 3 , 2 ,which pointresultsfrom themergingof A 3 and A 2 , 
are the same as those occurring in low carbon steels in passing through A 3 . 

IV. Changes at A t : As previously explained, the point A x occurs 
in all steels containing from a mere trace to .90 per cent, carbon. It cor¬ 
responds to the transformation of residual austenite into pearlite. At this 
point the following sudden changes in properties are noted: 1. A dilatation 
takes place which increases with the carbon content, reaching a maximum 
with .85% carbon. 2. Increased magnetism takes place for all steels on 
cooling through this point. 3. A marked decrease in electrical resistance 
is also noted on cooling through this range. 4. Below this point iron 
loses entirely its power to dissolve carbon. 5. The important changes from 
austenite to pearlite have already been shown to take place at Ai, but it 
is well to emphasize their significance here, for these changes give the key 
to the rational treatment of steel. The spontaneous transformation of 
austenite of eutectoid composition into pearlite, that is, a solid solution 




532 


CONSTITUTION OF STEEL 


into an aggregate of the eutectoid, makes possible the refining of steel by 
heat treatment, because on being heated through its critical range, the 
steel is changed from a coarse aggregate to a fine, almost amorphous, solid 
solution. This fact is also the secret of hardening steel, as will be shown 
later. 

Causes of the Thermal Critical Points in Steel: In seeking a cause 
for the existence of the thermal critical points in steel, all the phenomena 
exhibited must be considered. Starting first, then, with the thermal 
changes noted in the experiments previously described, it is well to note 
that there are but three well known causes of spontaneous evolution of 
heat in cooling bodies and of similar absorptions of heat on heating them. 
Briefly, these causes are (1.) the formation or decomposition of chemical 
compoimds; ( 2 .) changes of state, whether by solution or by the agency 
of heat; and (3.) allotropic or polymorphic transformations, which are 
always accompanied by either an absorption or evolution of heat when 
the substance of the body passes from one allotropic condition to another. 
As to the upper points, A 3 and A 2 , it has been shown that at these points 
even carbonless iron either absorbs or evolves heat, depending upon whether 
the metal is being heated or cooled while passing through the ranges. The 
fact that the iron is pure, nothing being present with which it could combine, 
and the fact that it is in the solid state throughout the experiment, preclude 
the possibility of either a chemical change or a change of state having 
taken place to cause the thermal changes indicated. Only the explanation 
founded on the basis of allotropy, therefore, remains. According to the 
two thermal changes that occur, then, pure iron or ferrite exists in at least 
three allotropic forms. Below the point A 2 it is called alpha iron, between 
A 2 and A 3 it is known as beta iron, while above A 3 it is said to be in the 
gamma form. While it is not desirable to undertake a discussion of this 
theory here, it may be pointed out that all the changes in properties pre¬ 
viously mentioned as accompanying these critical points are but additional 
evidence of the correctness of this view. Since the influence of carbon is 
to delay the separation of ferrite, it may be that beta iron is not formed 
on cooling steels containing .35% carbon or more, for since the temperature 
of the point Ar 3 - 2 in such steels is below that for the formation of beta 
iron, it is probable that just as iodine passes directly from the solid to the 
gaseous state by sublimation, or as amorphous sulphur at atmospheric 
temperatures passes to rhombic sulphur, so gamma iron passes directly 
to the alpha form. The fact that the point A! does not occur in carbonless 
iron and only faintly in low carbon irons, while with increase of the carbon 
it increases in intensity, is evidence that this point is due solely to the 
presence of carbon. Unlike the points A 3 and A 2 , which are due to allo¬ 
tropic forms of iron, A t is not due to any change in the carbon itself, but 
merely to the formation of pearlite, which implies the crystallization or 
falling out of solution of cementite, Fe 3 C, coupled with the complete 
change of the ferrite from the gamma to the alpha state as well. Above 














CRYSTALLINE STRUCTURE 


533 


Ai, the Fe 3 C, being in solution with the gamma iron and thoroughly diffused, 
has the power of imparting its own properties, hardness and brittleness, 
to the steel in a more pronounced way than when in the segregated form 
in which it occurs below Ai. Hence, formerly due to the theories then 
advanced to explain the hardening effect of carbon, the term hardening 
carbon was applied to it above Ai, while below Ai it was called cement 
carbon. 


SECTION III. 

THE CRYSTALLINE STRUCTURE OF STEEL. 

Crystals and Grains: That the crystalline structure of steel exerts 
a deep influence upon its strength and ductility is a well known fact. Since 
this structure lends itself to refinement through proper heat treatment, a 
clear understanding of all the laws governing the crystallization of steel 
is essential to the art of heat treating steel. When steel, like many other 
substances, passes from the liquid to the solid state, the process of solidi¬ 
fication is accompanied by crystallization, that is, the molecules of the 
various ingredients arrange themselves so as to form small bodies having 
regular geometrical outlines. Each of such bodies constitutes a crystal. 
In the case of iron in the gamma form the crystals are octahedra, or small 
eight sided bodies, but when the iron is in the alpha condition these crystals 
are cubic in form. Crystals have the remarkable property, called cleavage, 
of breaking most easily along certain planes usually parallel to the faces of 
the crystal. Hence, these planes of easy rupture are called cleavage planes. 
The direction of the cleavage planes constitutes the orientation of the 
crystal. Perfect crystals, called idiomorphic crystals, are formed only 
when the conditions are favorable. Thus, with high fluidity, absence of 
foreign particles, slow rate of cooling, and with the liquid at rest and 
undisturbed, perfect crystals of large size may form. Because of the unfavor¬ 
able conditions that usually prevail in its manufacture, the crystallization 
of steel results in the formation of imperfect crystals with irregular forms 
and smaller in size than perfect crystals. These imperfect crystals are, 
scientifically, designated as allotrimorphic crystals, but the metallurgist 
speaks of them simply as grains. 

Crystallization of Steel: As an aid to understanding the crystalliza¬ 
tion of steel it will, perhaps, be best to follow the crystallographic history 
of a steel casting that is allowed to cool slowly from the casting temper¬ 
ature to atmospheric temperature. For the present, let this steel be of 
any carbon content. During the solidification period, what has been 
termed the primary crystallization takes place, which consists in the 
formation of macroscopic tree-like bodies of austenite called dendrites. 
Each of these dendrites is composed of small octahedra, which is repre¬ 
sentative of the crystallographic form for austenite. Of these, Stead writes: 
“The fine fir-tree crystallites, containing probably a fraction of the amount 






534 


CONSTITUTION OF STEEL 


of the carbon in the liquid steel, grow steadily forward from the cold surface 
of the containing moulds. The crystallites develop branches in three 
directions corresponding to the axes of the cube, and these branches throw 
out similar branches themselves. Eventually parts of the most fusible 
portions are trapped between the branches and are the last to solidify. 
When there is much phosphorus or some sulphur in the metal, they are 
always present together with an excess of the carbon in the last residue 
of metal that remains liquid, and although in cooling down, after the liquid 
has solidified, the excess carbon diffuses out of it into the purer part, the 
sulphides and phosphides do not, but remain fixed, and can generally be 
detected in the solid metal.’’ 

As the solidification is completed a crystalline transformation, called 
granulation, sets in and continues until the critical range is reached, where 
all steels are found to be made up of grains, each grain having its own 
orientation and being made up of small octahedra of crystalline matter. 
The size of these grains varies with the rate of cooling, just as the rate of 
cooling affects the size of crystal in any metal. In passing through the 
critical range the structural changes are affected by the amount of carbon 
present, and for this reason it is best to consider the three grades of 
eutectoid, hypo-eutectoid, and hyper-eutectoid steels separately from this 
point onward. 

Crystallization of Eutectoid Steels: In the eutectoid steels the 
growth of the grains will continue down to the point Ar x , where the metal 
will be made up of grains of austenite containing ferrite and cementite in 
proper proportions to form pearlite. Therefore, in passing through the 
critical point, Ar x , each austenite grain changes bodily into a grain of 
pearlite. Hence, the coarse austenitic structure acquired by cooling from 
a high temperature gives rise to a correspondingly coarse pearlite structure. 

Crystallization of Hypo=Eutectoid Steel: As an example of the 
genesis of the crystalline structure of steels of hypo-eutectoid composition 
let a steel containing .60% carbon, corresponding to 72% pearlite and 28% 
free ferrite, be selected. In such a steel the granulation will proceed till the 
upper critical point Ar 3~2 is reached, where free ferrite begins to be rejected 
and continues till the point Ari is reached, when the residual austenite, 
being of the proper eutectoid composition, passes into pearlite as described 
for eutectoid steels. An important point to be noted here is the fact that 
this setting free of the excess ferrite is brought about through the rejection 
of ferrite in excess of the eutectoid composition by each individual grain 
of austenite, either to its boundaries or between its cleavage planes. 
When each grain of austenite becomes a gram of pearlite, the ferrite pre¬ 
viously rejected still remains as an envelope, thus forming the net-work 
mentioned under ‘ 'Ferrite.” Therefore, the structure of cast hypo-eutectoid 
steel is very coarse, for the following three reasons: 1. The slow and 

















CRYSTALLINE STRUCTURE 


535 


undisturbed cooling promotes the formation of large austenite grains and 
hence, later, of large pearlite grains. 2 . The slow cooling between the 
upper and lower critical points favors the rejection of a maximum amount 
of free ferrite, which rejection makes for coarseness of structure. 3 . The 
slow cooling from the upper critical point to atmospheric temperature 
promotes the crystallization of excess ferrite into large grains, especially 
when this excess is large in amount, i. e., in very low carbon steel. Because 
of its coarse structure, cast hypo-eutectoid steel is less tenacious and less 
ductile than forged, rolled or properly annealed steel of similar composition. 

Crystallization of Hyper=Eutectoid Steels: In the case of hyper- 
eutectoid steels, the granulation proceeds to the point Acm, a temperature 
that is indicated by the line Acm in Fig. 109, where excess cementite is 
liberated—like the excess ferrite in hypo-eutectoid steels. This excess 
cementite is rejected either to the boundaries of the austenite grains or 
between their cleavage planes, where, after the transformation of eutectoid 
austenite into pearlite, it remains to form a network about the grains of 
the latter. 

The Effect of Work on Grain Size: The effect of work on the 
mechanical properties of steel has been discussed in the second part of this 
book. It remains to be pointed out here that the greatest benefits of working 
as the steel cools to Ar! are due to a refinement in the grain size. The ex¬ 
planation for this refinement is found in the fact that, as each gram is 
distorted by the application of mechanical pressure, it endeavors to resume 
its original form, but being hindered in this by the rigidity of the mass, 
it breaks up into a number of smaller grains possessing the characteristic 
form. If the steel be worked at temperatures below Ar x , cold working, 
no refinement [of grain takes place, as the great rigidity of the metal or 
its lack of molecular energy prevents any readjustment of the grains at all. 
Hence, cold worked steel will show a pronounced distortion of grain. 

Crystalline Changes on Heating Steel: Since the preceding dis¬ 
cussions have been concerned mainly with steel under conditions of cooling, 
it may be profitable to review these changes from the standpoint of heating. 
Starting, then, with a low carbon steel, containing, say, .20% carbon, it 
will be found that, under normal conditions of manufacture and in its natural 
state, this steel consists of approximately 24% pearlite and 76% free alpha 
ferrite, the pearlite existing in small grains surrounded by the ferrite as a 
network. Upon heating through the point Aci, the pearlite changes into 
austenite, the iron of which is in the gamma form; but the free ferrite is 
still in the alpha form. As the heating continues throughout the zone 
bounded by Acj and Ac 2 the austenite thus formed begins to absorb the 
free ferrite. Upon passing through the Ac 2 range the remaining alpha 
ferrite changes into beta ferrite; and the steel as a whole will be found to 
be hard and non-magnetic. As the heating progresses through the second 
zone, lying between Ac 2 and AC 3 , the beta ferrite, which is only a remnant 






536 


CONSTITUTION OF STEEL 


of the original alpha ferrite, is gradually absorbed, so that as the range 
AC3 is passed the whole of the steel passes into the condition of austenite, 
or a solution of iron carbide in gamma iron. In a similar manner the changes 
in the constituents of steels of any carbon content up to eutectoid steel 
might be explained. In each case, however, it is to be noted that the 
temperature at which the transformations are completed falls as the carbon 
content is increased, being at its lowest when the eutectoid ratio has been 
reached. In the case of hyper-eutectoid steels, the free cementite is 
absorbed in a manner analogous to the absorption of free ferrite in hypo- 
eutectoid steels. But the final solution of the cementite takes place at 
a temperature range indicated by the line Acm, and much more slowly 
than ferrite. This latter point, being a matter of great practical importance, 
should be kept in mind. 

Crystalline Refinement on Heating: Besides these structural 
changes brought about by heating the steel through the various critical 
ranges, there still remains a matter of extreme importance to be explained. 
This matter refers to the crystalline, or grain, refinement observed when 
a steel is heated through these ranges. Again assuming that the steel is 
in a normal condition after manufacture in the usual manner, no change 
on heating is observed to take place in the grain structure until the tem¬ 
perature has reached that of the lower critical range, Aci- At this tem¬ 
perature, which marks the point where the original pearlite grains are 
transformed into austenite grains, the maximum refinement, that is, the 
smallest grain size possible, occurs. This refinement is to be expected 
from the conditions of the formation of the austenite. Since the conditions 
favorable for the formation of large grains require slow cooling from a high 
temperature, the formation of the austenite at this low temperature permits 
no growth of the grain structure at all. Hence, it is found to be almost 
amorphous in respect to its grain structure. But it is to be especially 
noted that, as the temperature is raised above this critical range, grain 
growth begins, which fact results in a gradual coarsening of the grain of 
the austenite as the temperature is progressively raised above this range. 
It is also to be noted that this increase in grain size not only varies with 
the temperature above the critical range, but also with the length of time 
at which the steel is maintained at the high temperature. In eutectoid 
steels, then, complete and maximum refinement of the grain takes place 
immediately the point Ac! is passed. But if the steel contains free ferrite 
or free cementite, that is, if it is of hypo-eutectoid or hyper-eutectoid 
grade, then the steel as a whole is not refined on passing Ac*, because the 
excess ferrite or cementite remains unaltered. In all cases it is only when 
all the constituents of the steel have passed into the state of a solid solution, 
or austenite, that complete refinement can be obtained. To bring about 
such a condition, it is necessary to heat such steels to a temperature a little 
above that of their upper critical ranges as indicated on the iron carbon 
diagram, on account of hysteresis previously discussed. 


















CRYSTALLINE STRUCTURE 


537 




1. Steel as cast and cooled 
naturally. 


2. Heated to 927° C. and 
quenched in water. 


Fig. Ill Natural Size Photographs Showing Effect of Heat Upon the Grain Size of 
Cast Steel. Specimens, left to right, contain, .25% Carbon and .36% Carbon. 

Practical Importance of Grain Structure: The proper refinement 

of grain structure is of great practical importance. An illustration of the 

way in which the facts pointed out above in connection with the effects 

of mechanical work and heat upon the grain structure of steel may be prac- 


1. Heated to about 1300° C. 
arid quenched in water. 


2. Heated considerably above 
the critical range and quenched 
in water. 


3. Heated to just above the 
critical range and quenched in 
water. 


4. Heated to just below the 
critical range and quenched in 
water. 


5. Steel as forged and cooled 
in air to atmospheric temperatures. 


Fig. 110. Natural Size Photographs Showing Effect of Heat Upon Grain Size of a 
Rolled and Forged Steel, Carbon .75% (Metcalf’s Experiment). 










CONSTITUTION OF STEEL 


538 


tically applied is furnished by the welding of steel. If two steel bars are 
welded together by scarfing the ends slightly and hammering lightly over 
the weld only, as is the practice of most blacksmiths in welding iron bars, 
it is found that, while the weld itself is strong, the welded bar will be weak 
on each side of the weld. A bending test applied to such a weld generally 
causes the bar to break a short distance from the weld, which fact is 
responsible for the assertion, often made by some blacksmiths, that the 
weld is stronger than the bar. A careful examination of the whole bar, 
however, will usually show that the regions on each side of the weld are 
the weakest points in the entire bar. Evidently this weakness has been 
developed in the process of welding. The high temperature required in 
welding increases the grain size of the ends to be welded for a considerable 
distance along the bars. The subsequent hammering refines this large 
grain in the weld itself, but not in the areas on each side of it. By changing 
the manner of welding somewhat, the structure of the welded bar can be 
made almost uniform throughout, and these defective areas will not appear. 
This result can be accomplished by making the weld in the following 
manner, which is the usual practice in welding steel: The two ends to be 
welded are first heated to a moderate forging temperature for a distance 
of several inches back, the exact distance depending upon the size of the 
bar; these ends are then stove up, or upset, that is, the heated regions 
are shortened and thickened by hammering directly against the ends. 
Next, the ends are scarfed, but instead of a short, blunt scarf sometimes 
used, a well beveled scarf should be made. The scarfed ends are then 
heated to a welding temperature; a flux of common river sand or a reliable 
commercial welding compound is applied; the weld is made as usual; and 
the thickened portion of the bar is forged down to a size conforming to the 
remainder. This forging refines the grain which had previously been made 
coarse by the heating, and restores the uniform structure of the bar. If 
the bars have been stove up right in the beginning, the form of the weld 
will be such as to require the greatest amount of forging where the grain 
is the largest and will decrease to none where the steel was heated only to 
the critical range. 


Summary of Chapter I. The conditions and properties of the iron 
carbon alloys and their constituents may be summed up about as follows: 
Above the critical ranges, the iron is in the gamma form, and the carbon 
is dissolved, thus imparting to the alloy, when the carbon is present to the 
amount of about .30%, the power of hardening; the alloys are non-magnetic 
and crystallize on cooling slowly, but mechanical working prevents the growth 
of the crystals and reduces their size. Below the critical range, the metal 
represents an aggregate of ferrite and cementite, Fe 3 C, and it possesses little 
hardening power. Here the iron is in the alphaform, the alloys are magnetic, 
no crystallization takes place, and mechanical working distorts the grain 
structure. 





THE TREATING OF STEEL 


539 


CHAPTER II. 

HEAT TREATING THEORY AND PRACTICE. 

Introduction: While considerable time has now been spent in a 
discussion of subjects that may appear to be purely theoretical in nature 
and of little practical value, yet this course is justified, because the principles 
explained form the basis of all heat treating processes, and a clear under¬ 
standing of them is therefore essential. The practical application of these 
principles will now be considered under the following headings, correspond¬ 
ing to the three chief processes of heat treatment as explained in the 
beginning. 


SECTION I. 

ANNEALING. 

The Annealing Operation consists in (1) heating the steel to some 
predetermined temperature, (2) keeping the temperature constant at the 
predetermined point for a given length of time, and (3) cooling the steel 
according to some predetermined course to atmospheric temperature. To 
accomplish the desired result in the given steel to be treated requires that 
all three of these steps in the annealing operation be very carefully planned 
and as carefully carried out, for the success of the operation depends entirely 
upon the proper correlation of the rate of heating, the temperature to which 
the steel is heated, the time it is kept at the annealing temperature and 
the rate of cooling. 

Purpose of Annealing: Evidently, then, the annealing operation will 
be modified to suit the end sought. In general, the purpose of annealing 
may involve any one or all of the following aims: 1. To soften the steel 
in order that it may meet certain physical requirements or be more easily 
machined. 2. To relieve internal stresses and strains induced by forging, 
rolling, or drawing, or by a non-uniform contraction in cooling. 3. To 
remove coarseness of grain and thus secure a more desirable combination 
of strength, elasticity and ductility for resisting the stresses to which it is 
to be subjected in service. The treatment is generally applied (1) to hot 
forged steel objects, because their grain structure is often more or less 
heterogeneous and, owing to high finishing temperature, relatively coarse; 
(2) to cold worked steel, such as sheets and cold drawn wire, which often 
must be annealed in order to increase or restore its ductility; and (3) to steel 
castings, which usually have so coarse a grain structure as to be very 
deficient both in strength and ductility. 





/ 


w. 


540 THE TREATING OF STEEL 


True Annealing and “Process” or “Works” Annealing: To accom¬ 
plish the results sought as expressed above in aims (1) and (2), it is not 
always necessary to heat the steel to the critical range. Thus, in the 
“process” or “works” annealing employed in wire drawing, it is only 
necessary to heat the steel, which contains less than .10% carbon, to about 
550° C. in order to relieve the strained condition of the ferrite and restore 
the ductility. The same is also true in the case of the “white annealing” 
of cold rolled sheets. It is to be noted, however, that this treatment does 
not develop the maximum softness, because the pearlite is not affected. But 
as this constituent is present in so small amounts, its influence is scarcely 
evident. This method is also sometimes applied to tool steels in order to 
soften them for machining. All true or full annealing, however, requires 
that the steel be heated to a temperature above that of its upper critical 
range, and it is to this true annealing the following discussion is to be 
confined. 

Heating for True Annealing: The first step in the annealing 
operation is to heat the steel past its critical range, for in so doing the 
previous structure is completely obliterated and a new one, nearly amor¬ 
phous, is born. As has been previously explained, this important change 
is due to the passage of the steel structure from the state of an aggregate 
of ferrite and cementite to a homogeneous solid solution. Should the steel 
remain below the critical range, no structural change takes place, if the 
case of strain relief noted above in cold worked steel be excepted. The 
coarsening effect upon the grain size of steel, brought about by heating 
above this range, has already been explained. The proper temperature, 
then, for true annealing is one but slightly above the critical range of the 
steel, and this temperature must be maintained uniformly as near the 
range as possible during the time the steel remains at the annealing 
temperature. 

The following ranges of temperatures are recommended by the committee 
on heat treatment of the American Society for Testing Materials. 


# TABLE 59. Annealing Temperatures as Recommended by the 
American Society for Testing Materials. 


Range of Carbon Content. 

Less than 0.12 per cent. 
0.12 to 0.25 per cent. 

0.30 to 0.49 per cent. 

0.50 to 1.00 per cent. 


Range of Annealing Temperature. 

875 to 925 degrees C. 

840 to 870 degrees C. 

815 to 840 degrees C. 

790 to 815 degrees C. 


These temperatures are shown diagramatically in the accompanying 
figure, together with recommendations by other authorities. 



ANNEALING 


541 



Per Cent. Carbon 

Fig. 112. Annealing (and Hardening) Ranges Showing Approximately the Temper¬ 
atures Recommended by Different Authorities. 


Legend. 

.. Sauveur (for treating forgings). 

. American Society for Testing Materials. 

. Bullens (for annealing and hardening). 

Stead’s Lower Curve (for refining and hardening). 
Stead’s Upper Curve (for annealing and normalizing). 






































































































542 


THE TREATING OF STEEL 


In large bodies, the central portion will lag in temperature behind the 
exterior, hence such objects should be heated very slowly, for very evident 
reasons. The practice of raising the temperature of the furnace beyond 
the proper annealing temperature in order to drive the heat to the interior 
of the piece is a great mistake, for then the temperature of the exterior 
may be carried beyond the proper point with consequent evil results 
attending. 

Importance of Time in Heating for Annealing: The time the object 
should remain at the annealing temperature is governed largely by its size. 
Evidently, it should be maintained at this temperature until it has become 
uniformly heated throughout. The committee quoted above recommends 
that an exposure of one hour is sufficient for pieces twelve inches thick. In 
practice, however, it is often necessary to keep the object at the annealing 
temperature for a much longer period than that indicated by the committee 
or that which theoretically would appear sufficient. This is especially 
true with plain steel in cases where the mechanical work upon the steel has 
been severe, or where the steel has been improperly heated in working, and 
in certain of the alloy steels. It has been shown by Bullens 1 “that the 
greater the internal stress upon the steel the greater is the amount of lag, 
or final release, of this stress behind the actual change of constituents. 
That is, even though a totally new structure may be formed by the anneal¬ 
ing temperature, there remains for a considerable length of time a tendency 
of the new structure to return, upon slow cooling, to the stressed condition of 
the original, even though the constituents themselves may be those born 
at the new temperature. It is important, therefore, if a soft steel 
free from all internal stresses and strains is desired, that a sufficient length 
of time be allowed for the permanent elimination of these stresses and 
strains, before cooling.” To accomplish this result a period of time 
extending over several hours, or even days, may be required. 

Cooling: Having, thus, by proper rate of heating and length of time 
of heating, obtained the steel in a state favorable to maximum refinement, 
the next step is to cool it properly. As variations in the rate of cooling 
produce very profound effects upon the physical properties of the metal, 
this process is not as simple as it appears. The effects of cooling at different 
rates and in different ways should, then, be carefully studied. The property 
most noticeably affected by the cooling process is the hardness. As is 
well known, this property in a given steel depends upon the rate of cooling 
from above the critical range. Thus, by the most rapid cooling, it is possible 
to develop the maximum hardness, or by the slowest cooling the greatest 
softness, and by varying the rate of cooling any degree of hardness between 
these extremes may be obtained. In searching for a reason for these changes 
in properties, it is not surprising that investigators have found that 
important structural changes accompany all cooling, and that these changes 
vary, in the effects they produce, with the speed of the cooling. 


iSteel and Its Heat Treatment, Second Edition, pp. 133 to 148. 




ANNEALING 


543 


Effect of Cooling on the Net Work: The first of these structural 
changes that may be mentioned is the effect of different rates of slow cooling 
upon the net work of ferrite described in the preceding section of this book. 
Thus, in very slow cooling of hypo-eutectoid steels from the annealing 
temperature a coalescence of the excess ferrite into large grains intermingling 
with coarse pearlite grains results. If the steel be now cooled rather rapidly, 
but still not so rapidly as to prevent the formation of pearlite, the excess 
ferrite will be found to be of a fine grain structure and to form a fine network 
about the pearlite. If, now, these two methods be combined, that is, if 
the cooling be made to proceed rapidly through the upper part of the trans¬ 
formation range then slowly to atmospheric temperature, the net work of 
ferrite is fine, but the pearlite is better developed than in the second 
case. 

The Effect of Cooling Upon Pearlite now remains to be explained. 
While the rate of cooling from below the critical range can have no effect 
upon the pearlite, changing the rate of cooling while the steel is passing 
through this range and the solid solution is being transformed into pearlite 
will correspondingly change the arrangement of the ferrite and cementite 
composing the pearlite, so that the same steel may be made to exhibit 
widely differing physical properties. As mentioned before, the austenite 
does not pass directly into the pearlitic condition on cooling through the 
critical range, but makes the change by way of the three transition stages 
known as martensite, troostite, and sorbite. Of these, only sorbite is 
retained in the steel by annealing methods of cooling. In small sections 
it is retained by air cooling through the lower critical range. By varying 
the cooling through this range this change from sorbite to pearlite may 
be controlled so as to produce five phases, or varieties, of pearlite having 
different physical properties as follows:— 

1st Phase. True Sorbite with emulsified FegC. Very dark on etching. 
Tensile strength, 150,000. Elongation, 10% in two inches. 

2d Phase. Sorbitic pearlite with semi segregated FesC. Dark on 
etching. Tensile strength, 125,000. Elongation, 15% in two inches. 

3d Phase. Finely laminated pearlite with FesC almost completely 
segregated. Exhibits a play of gorgeous colours when lightly etched. 
Tensile strength, 100,000. Elongation, 10% in two inches. 

4th Phase. Fully laminated pearlite with completely segregated FeaC. 
Tensile strength, 85,000. Elongation, 8% in two inches. 

5th Phase. Massive pearlite, consisting of coagulated FesC and 
ferrite. Tensile strength, 75,000. Elongation, 5% in two inches. 

The second phase is the one sought in the process of patenting in wire 
drawing. So, it is seen that, having obtained the greatest possible refine¬ 
ment as to grain size and released all the internal stresses and strains in the 
metal by heating to the proper temperature, it still remains to adjust the 
physical properties by regulating the rate and the manner of cooling. 




544 


THE TREATING OF STEEL 



' i" v ' . ‘ - 

1. Sorbite. Cementite is emulsified. 
Obtained in steels of low carbon content by 
cooling rapidly to atmospheric temperatures. 



2. Sorbitic Pearlite. Cementite is partly 
segregated. Obtained by cooling rapidly through 
the upper range only. 

■ ■ f 

;i . . > j■ j. 1 . „ . • ,<•« 

• . . . : , 


3. Pearlite. Cementite is largely segregated. 
Obtained by moderately slow cooling. 

'■ ■ 1 - 


4. Laminated Pearlite. Cementite is com¬ 
pletely segregated. Obtained by slow cooling. 




5. Massive Pearlite. Cementite and ferrite 
are coagulated. Obtained by very slow cooling 
to atmospheric temperatures. 


Fig. 113. Microphotographs Showing Progressive Segregation of Cementite in the 
Development of Pearlite from Sorbite. (White areas represent ferrite, black 
areas, cementite.) 







ANNEALING 


545 


Other Factors to consider in cooling are the carbon content and the 
size of the object. In general, the lower the carbon the more rapid may 
be the rate of cooling without affecting to any marked degree the softness 
and ductility of the metal. For example, steels containing less than .15% 
carbon may even be quenched in water, and those containing less than 
.30% carbon, in oil, without markedly decreasing their ductility. In order 
to secure the same rate of cooling in objects of different size, it is obviously 
necessary to regulate the external conditions in accordance with the dimen¬ 
sions of the objects treated. Thus, the cooling in air of a very fine wire 
may be equivalent to quenching in oil or water an axle of the same carbon 
content. 

Methods of Cooling: In general, there are three methods of cooling, 
namely, furnace cooling, insulated cooling and air cooling. Of these, furnace 
cooling may be made the slowest, especially if the furnace is large and can 
be effectually sealed from air draughts. This method gives maximum 
softness and ductility. In other words, the tensile strength and elastic 
limit will be at their lowest, while the elongation and reduction in area 
will be at or near their maxima. Steel subjected to such treatment will 
resist severe distortions. In what has been termed above as insulated 
cooling, the object is removed from the furnace and covered with a blanket 
of lime, sand, ashes, etc., or it may be placed in a brick or concrete lined 
underground pit with a tight fitting cover, which in turn may be covered 
with ashes or loose earth. In cases where large amounts of steel are placed 
in a single pit, this method may be slower even than furnace cooling. In 
air cooling, the object is simply removed from the furnace and allowed to 
cool in the air. Evidently, the rate of cooling by this method will be affected 
by the size of the piece and the season of the year. In addition the physical 
properties imparted will depend somewhat upon the carbon content. Hence, 
the American Society for Testing Materials recommends that * ‘Thick 
objects with less than 0.50% of carbon may be cooled completely in air, 
of course, protected from rain or snow. Objects with 0.50% of carbon or 
more, and thin objects with from 0.30% to 0.50% of carbon, may be cooled 
in air if their cooling is somewhat retarded, as for instance, by massing 
them together, as happens in the case of rails.” The effect of the more 
rapid cooling in air is to increase the strength and elastic limit, but lower 
the reduction and elongation. In order to hasten the cooling, articles of 
low carbon content are sometimes immersed in water after they have 
become black in color. This method is then called water annealing. 

Combination Methods of Cooling: Besides the three general 
methods of cooling described above, various combination methods have 
been employed with great success. Three of these, as directed by Bullens, 
are as follows: 

1. “Heat to slightly over Ac 3 , air cool to just over Ar^ return to a 
furnace which is held at that temperature (about 725°C.), heat until 




546 


THE TREATING OF STEEL 


uniform, and then cool slowly. The latter heating should not be any 
longer than is possible. This method will tend to prevent the formation 
of large amounts of free ferrite, but will affect the pearlite, as there will 
be slow cooling through the Ar x range. 2. Heat to slightly over the AC 3 
range, air cool to just under the Ar x range, return to a furnace and heat to 
730° C. and slow cool. This method will effect a greater toughening, if 
the temperature has not been prolonged too greatly at the second heating. 
3. Heat to slightly above AC 3 air cool to below Ar 1? return to a furnace 
heated at a temperature slightly below Ar x (660° to 670° C.), hold at this 
temperature until uniformly heated, and slow cool (in lime or air). By 
permitting the steel to air cool to a temperature below the lowest trans¬ 
formation, advantage is taken of any ‘hardening effect’ or retardation in 
the transformation of austenite into a conglomerate of pearlite and ferrite. 
This effect will increase with the percentage of carbon and the smaller the 
size of the piece. The reheating to a temperature below the lower critical 
range, if not prolonged, will neither change the grain size nor allow of the 
coalescing of the excess ferrite or of the individual constituents of the 
pearlite, but will form a mass of irresolvable and intermixed pearlite and 
ferrite known as ‘sorbite.’ At the same time, however, it will give the 
maximum combination of large ductility, good strength and excellent 
machining properties. This method is of particular value in the annealing 
of tool steels, in which it has given most excellent results.” 

Double Annealing consists in heating the steel to a temperature con¬ 
siderably over the AC 3 point, cooling rapidly to some point below the 
lower transformation range, then immediately reheating to a point slightly 
under or over Ac*, and finally cooling slowly. This method is employed to 
relieve the most severe strains, which do not respond readily to ordinary 
annealing. The high first annealing temperature effaces the strains, while 
the rapid cooling prevents their returning. As this cooling tends to harden 
the metal, the second process is necessary to soften it and refine the grain, 
coarsened by the first operation, as much as possible. The second heating, 
of course, may be to a temperature just above AC 3 , when even better results 
should be obtained, provided softness is the chief end sought. 

Box Annealing: In many instances, especially with tool steel, it is 
important that the surface be protected from oxidation, or decarbonization. 
Some furnaces are now designed so that the object being heated may be 
surroimded by a reducing atmosphere, and so oxidation is prevented. Where 
such furnaces are not provided, it is the practice to pack the object in a 
metal box, called an annealing box, with some refractory material, such as 
sand, groimd mica, etc., in the case of low carbon steel, or with some reducing 
substances, as for example a mixture made up of a little charcoal with 
ashes, burned bone, etc., in the case of higher carbon steels, like the tool 
steels, for example. 



ANNEALING 


547 


Annealing Hyper=Eutectoid Steels: In annealing hyper-eutectoid 
steels, as in the case of hypo-eutectoid steels, one or more of these objects 
are aimed at; ( 1 ) release of strains, ( 2 ) softening in preparation for machin¬ 
ing, and (3) change of structure. The first object may be accomplished 
by a simple reheating at temperatures considerably below those of the 
critical range. The second and third objects are more difficult to attain, 
for the treatment administered will be governed by the amount of the excess 
cementite and the form in which it exists. Thus, if the cementite is partly 
diffused, that is, does not exist as a net work or as spines and needles, and 
the grain size is small, conditions that may generally be expected in high 
carbon tool steels, the forging hardness may be largely removed by anneal¬ 
ing at a temperature slightly under Ac. or between 600°C and 700°C. The 
steel should not be kept at this temperature any longer than is necessary to 
heat it thoroughly and uniformly throughout, as prolonged heating may 
cause the excess cementite to coagulate. Such treatment will release the 
strains and soften the steel sufficiently for machining. On the other hand, 
if the grain is coarse, making a complete change in structure desirable, it 
will be necessary to heat to a temperature in excess of the Aci-2-3 point, or 
above 725 °C. For steels with a carbon content approximating 0.90%, such 
heating will bring about a complete change of structure and give the finest 
grain-size obtainable through annealing. For steels with a carbon content 
considerably in excess of the eutectoid ratio the annealing may be done at 
similar temperatures, provided the excess cementite is more or less in 
solution. If the cementite is not in solution and a maximum refinement is 
desired, the steel may be oil quenched from a temperature somewhat over 
the Aci-2-3 range, and subsequently annealed at a temperature just below 
that range, or it may be normalized and annealed. 

Normalizing and Spheroidizing: These are two processes applied to 
hyper-eutectoid steels in particular, though normalizing is often applied to 
hypo-eutectoid steels also. If the free cementite in the former steel exists 
as a network or as spines, which would make the steel difficult to machine, 
annealing at the usual temperatures (Aci- 2 - 3 ) will not affect this cementite, 
but will simply refine the ground mass. In order to eliminate this free 
cementite, it is necessary first to normalize, that is, quench the steel from 
a temperature above that of the Ac cm range. Usually, air cooling from 
a temperature of,say,960° C., or 1000 ° C., will not permit the cementite 
to recoagulate. Lower carbon steels are heated to about the same tem¬ 
perature, but quenching is never required. Hence, in practice, normalizing 
usually consists in heating the steel to the temperatures mentioned and 
cooling simply in air. dhe annealing may then be carried out ai a tem¬ 
perature of 745° C. or over, to secure the refining of the grain size and 
complete softening of the steel. The heating for annealing should be just 
as short as possible in order to prevent the separation of the excess cementite 
again. The method given above maybe modified for hyper-eutectoid steel 
by annealing at a temperature slightly under the lower critical range instead 




548 


THE TREATING OF STEEL 


of over it. This method, however, is subject to the objection that the steel 
will not be refined, but will possess a large grain size on account of the high 
normalizing temperature. But on the other hand, the lower annealing tem¬ 
perature entirely prevents the formation of free cementite either as spines 
or as a network, and the excess cementite is thrown out, under these con¬ 
ditions, as little nodules or “spheroids,” if the reheating temperature has 
been near the end of the lower critical range. Spheroidal cementite may 
also be obtained by cooling very slowly through the end of the Ar* trans¬ 
formation range. Spheroidizing is a great help in the machining of high- 
carbon steels. 


SECTION II. 

HARDENING. 

The Hardening Operation: The operation of hardening as applied 
to steels containing a sufficient amount of carbon consists fundamentally 
of the two operations of heating to a suitable temperature and suddenly, 
or rapidly, cooling. The heating may be accomplished in a number of 
ways, varying from costly and specially designed furnaces and baths heated 
with gas or electricity to the simple forge fire of the blacksmith; but the 
cooling is always brought about by plunging the steel into a suitable liquid, 
a process called quenching. Let the means be what they will, in properly 
hardened steel the original structure, as it existed before the hardening 
process, such as coarse grain size, network, etc., has entirely disappeared 
and has been replaced by a new structure, totally different from that of the 
unhardened steel. To understand thoroughly the hardening process a close 
study of the two operations by which these changes are brought about 
should be made. 

Heating for Hardening: The structural changes that accompany the 
heating of steel through its critical ranges have already been briefly 
described. Graphically, these changes are represented in the central part of 
the accompanying diagram (Fig. 114), depicting the heating and cooling of a 
steel with a carbon content of about .90%. From this evidence it will be 
seen that the function of the heating is to bring about the proper change in 
structure so as to obtain (1) the formation of the hard constituents of the 
steel and (2) the smallest grain size, or highest refinement of the crystalline 
structure. From what has already been said, these structural changes can 
be obtained only by heating the steel above its critical range. Any attempt 
at hardening it at a temperature inferior to this range results in only a very 
slight, if any, increase of the hardness. Again, the metal should not be 
heated much above the top range, for then its grain structure is coarsened, as 
has been previously explained, also, and no additional hardness is imparted. 
Clearly, the best temperature to which the steel should be heated is one 
just above the critical range. The proper temperature to which plain 
carbon steels should be heated is the same as for the true annealing of the 
same steels. What has been said about the rate of heating and the influence 





HARDENING 


549 


of size of section in annealing also applies to heating for hardening. 
If any difference, additional emphasis should be placed on the uniformity of 
heating. The rule for heating may be put thus: Heat slowly, uniformly, 
and thoroughly, to the lowest temperature, and no higher, that will give 
the desired results. To meet these requirements, the final heating of steel 
for hardening is often, and commendably so, conducted in baths of molten 
lead or of the chlorides of sodium, calcium, potassium or barium. 






Effect of cooling at different 
rates from above the critical 
range. 


Effect of rapid cooling from 
different points relative to 
the critical range. 



• A:' 

m 

MM 

H 

B 

n. 

'K 


Legend: P=Pearlite, A=Austenite, M=Martensite, T=Troostite, 
S=Sorbite. 

Fig. 114. Diagram Depicting the Different Methods by Which the Five Different 
Structural Constituents of Eutectoid Steel May Be Obtained. (After Sauveur.) 


Cooling for Hardening: Thus it is seen that heating for both anneal¬ 
ing and hardening are very similar, and that the changes wrought in the 
microscopic constituents of the steel are the same in both cases. The main 
difference in the two operations is found in the rate of cooling through the 
critical ranges, at least. For hardening, this cooling must be very rapid, 
whereas in annealing it was characterized as slow. The transitions attend¬ 
ing the transformation of austenite to pearlite on slowly cooling through 
the critical ranges have been described. It will be recalled that this trans¬ 
formation is not instantaneous, nor is it direct, but takes place by stages 
through transitional structures called martensite, troostite, and sorbite, 
the order on slow cooling being from austenite, to martensite to troostite, 
to sorbite, to pearlite. On heating, this order is reversed. It now may 
be explained that the secret of the hardening process is revealed by the 
fact that rapid cooling through the critical range may prevent this trans¬ 
formation in part or in whole, depending on the rate of the cooling. Thus, 
by the most rapid cooling, the steel at atmospheric temperatures may 
consist largely of austenite, while a little slower cooling produces 
martensite; still slower, troostite; slow, sorbite; and very slow, pearlite. 
Incidentally, it may be remarked that the constituents found in the 
steel after treating also depends on the temperature within the critical 


















































550 


THE TREATING OF STEEL 


range at which the rapid cooling begins and the carbon content of the steel, 
because these constituents are formed at different temperatures and the 
presence of carbon retards the transformation. Since the properties of the 
cooled steel are imparted to it by the constituent which predominates, a 
study of the characteristics of these transitional constituents will, there¬ 
fore, be of value. For the sake of brevity and convenience, this knowledge 
is here put down in tabulated form. 


Table 60. Data with Reference to the Constituents of Hardened Steel. 


Name 

Nature 

Occurrence 

Temperature of 
Stability 

Structure 

Physical 

Properties 

Austenite 

Solid solution of 
FeaC in gamma 
iron, Carbon 
content from 
trace to 2%. 

Obtained in 1.50% 
C. steels when 
quenched in ice 
water from 1050° 
C. Occurs in steel 
containing 12% 
Mn. and 25% Ni. 
even after slow 
cooling. 

Normally in 
region between 
A-l, 2, 3, and A 
cm. Becomes 
pearlite on cool¬ 
ing slowly past 
Ai: more rapid 
cooling forms 
martensite. 

Polyhedral 

grains 

Varies with car¬ 
bon content. 
Very hard but 
softer than 
martensite. 

Martensite 

Solution of Fe 3 C 
in beta iron, 
Carbon content 
from trace to 
1%. 

Obtained easily by 
quenching small 
bodies of hyper- 
eutectoid steel, in 
cold water. More 
difficult to obtain 
in low carbon 
steels. Chief con¬ 
stituent of hard¬ 
ened carbon tool 
steels. 

Normally at 

slightly lower 
temperature 
than austenite. 
Changes into 
troostite. 

Fibers or hat 
plates lying par¬ 
allel to three 
sides of a tri¬ 
angle. 

Varies with car¬ 
bon content. 
Hardest con¬ 
stituent of steel 
of eutectoid 

composition. A 
little less hard 
than cementite. 

Troostite 

Mixture of FesC 
in beta iron 
crystallized 
FesC and crys¬ 
tallized alpha 
iron. 

Obtained by re¬ 
heating marten¬ 
sitic steel to 400° 
C. or on cooling 
relatively slowly 
through critical 
range. Found in 
center of large 
objects quenched 
in water. 

Normally at 
lower temper¬ 
ature than mar¬ 
tensite. 

Slightly granular 
with sorbite and 
martensite in¬ 
termingled and 
with ferrite and 
cementite in 
hypo-and 
hyper -eutectoid 
steels. 

Intermediate be¬ 
tween marten¬ 
site and sorbite. 
Not so hard as 
martensite but 
stronger and 
more ductile. 


Neither pearlite nor sorbite are, strictly speaking, constituents of 
hardened steel, but the latter, on account of its position in the transforma¬ 
tion scale, forms the connecting link between hardened and annealed steel, 
hence may occur in both. The nature^and properties of sorbite have already 
been given, and it should here be recalled that it is the toughest constituent 
of steel. The transition from austenite to pearlite is admirably illustrated 
in the preceding diagram of figure 114. 








































HARDENING 


551 


Cooling or Quenching Media: Since the rate of cooling controls 
the hardening process, the selection of the proper quenching medium is a 
matter of much importance. The withdrawal of heat, the only function 
of a quenching liquid, from the metal immersed in it depends upon its 
quantity, its specific heat, its conductivity, its viscosity, its volatility, its 
latent heat of vaporization, and, to some extent, its initial temperature. 
The quantity and specific heat of the liquid control the quantity of heat 
the bath can absorb with a given rise in temperature. The viscosity affects 
the flowing properties of the liquid, hence the convection of heat by it, and 
therefore is a factor in the cooling properties of the liquid, for it is by con¬ 
vection and conduction that the heat is carried away from the steel to 
distant parts of the bath. The volatility indicates the temperature at 
which the liquid will become a vapor and form bubbles of gas on the 
surface of the steel, which tend to retard the cooling. Evidently, if the 
latent heat, or heat of vaporization, is high the volatility may be relatively 
low, for then much heat is required to change the liquid to the gaseous 
state. Since the speed at which heat is transferred from one body to 
another varies directly as the difference in their temperatures, it is evident 
that the initial temperature of the quenching liquid must affect the rate 
of cooling. Thus, water, one of the most efficient media for rapid cooling 
in use commercially, has high specific and latent heats, and its viscosity 
is very low, properties favoring its cooling power, while its volatility and 
conductivity are both low, properties against it as a quenching agent. 
Then just next to water in cooling power comes mercury, which has a lower 
specific heat, a lower heat of vaporization and higher viscosity than water; 
but it is less volatile and is a very much better conductor of heat. Thus, 
while the one owes its cooling power to one set of properties, the other is 
almost as efficient because of an altogether different set. A solution of 
salt in water, brine, is a little more rapid than water, while water sprayed 
under pressure upon the metal is a quicker cooling agent than either water 
or brine. After water, the chief quenching media in use commercially are 
the oils, all of which are much slower than water. An interesting experi¬ 
ment reported by Messrs. Matthews and Stagg 1 is intended to show the 
quenching properties of the various liquids that are employed in com¬ 
mercial hardening. In this experiment a suitable test piece of steel was 
carefully heated to 1200° F. and quenched in 25 gallons of the medium 
under examination, and the time required to cool the steel to 700°F. noted 
with a stop watch, as well as the rise in temperature of the medium. In 
each medium this operation was repeated successively imtil the medium 
had either reached its boiling point or a temperature of 250° F. The results 
of this experiment were then plotted somewhat as shown in the accom¬ 
panying diagram. 

Combination Methods of Quenching: Besides the straight water or 
oil quenching and water spraying, many special quenching methods and 
media have been tried. Many of th e latter are fakes, but the three follow - 

iSee “Factors in Hardening Tool Steel” by Matthews and Stagg. American 
Society of Mechanical Engineers, 1915. 








552 


THE TREATING OF STEEL 


ing special methods of quenching have proved of great value. Thus, when 
high tensile strength is required, yet on account of the size of the piece or 
the chemical composition—manganese too high, for example—water 
quenching is unwise, the bath of water may be covered with oil to an equal 
depth, so that the piece upon being lowered into the bath is partly cooled 
in this oil, which then forms a film over the surface that retards the cooling 
by the water somewhat. This method is sometimes applied to large 
forgings, such as axles. For small tools a thin film of oil on the water 
suffices. Another method, used by some tool hardeners, consists of first 
plunging the tool into water to remove a part of the heat, then into oil till 
the cooling is complete. Information as to what is aimed at by this method 
is not at hand, but it is evident that the method is not so severe as straight 
water cooling. Where great toughness with little hardness is required, the 
article may be plunged into and forcibly submerged in molten lead, as this 
manner of quenching produces sorbite in steels under the eutectoid in 
composition. 



Time in Seconds Required to Cool Test Piece from 1200° F to 700° F. 

Legend: 


6— New Bleached Fish Oil. 

7— New Cotton Seed Oil. 

c, -t, • ^..i/60% Cotton Seed. 

^TemPenng O.l{ 40 o| MineraL 

9—Mineral Tempering Oil. 

10— Dark Mineral Tempering Oil. 

11— Very Viscous Tempering Oil. 
Note. 10 and 11 are similar to cylinder oils. 

Pig. 115. Diagram Illustrating Approximately the Quenching Power of Various 
Liquids. (Data by Messrs. Matthews and Stagg). 


B—Brine. 

W—City Water. 

1— New Fish Oil. 

2— No. 2 Lard Oil. 

3— Lard Oil in Use Two Years. 

4— Boiled Linseed Oil. 

5— Raw Linseed Oil. 













HARDENING 


553 


Manner of Quenching: Much skill is required on the part of the 
operator in the quenching of steel to prevent cracking and warping. Both 
defects are due to unequal or non-uniform cooling of the different parts of 
the piece, and are more liable to occur, for obvious reasons, in bodies of 
large size or of irregular section. It is to overcome this danger that large 
axles are hollow bored before treatment. All large sections, if solid, must 
be reheated immediately after hardening in order to relieve the internal 
stresses and strains, else incipient fractures will result. Warping will 
always occur in small sections, if the quenching is not uniform. As warping 
more often results when the piece is plunged into the quenching bath at an 
angle, it is always best to quench vertically, in the direction of greatest 
length, whenever such procedure is possible. 

Progressive Hardening: Progressive, or differential hardening, is 
accomplished by quenching only a part of the object. In such a method the 
heat is slowly withdrawn from the part furthest from the quenching liquid, 
but more and more rapidly as the part quenched is approached, so that 
the steel becomes progressively softer and tougher from the hardened part. 
By withdrawal of the piece before cooling is complete, the heat in the 
unquenched part may be made to temper the hardened portion. In this 
method care is needed to avoid hardening, or quenching, rings, which form 
if the piece is held in the quenching bath at a uniform depth. To avoid 
them the piece should be raised and lowered during the quenching. This 
method is employed in treating such tools as anvils, die blocks, edged 
tools, pointed tools, etc. 

Hardening Eutectoid Steels (C. .80 to 90%): Steel of eutectoid 
composition possesses the maximum hardening power, that is, the difference 
in hardness between the quenched and unquenched article of eutectoid 
composition is greater than that in any other grade of the plain steels. So, 
this statement does not mean that quenched eutecoid steels are the hardest 
steels, for hyper-eutectoid steels may show much greater hardness both 
before and after hardening than eutectoid steels, due to the presence of 
free cementite or to more highly carbonized martensite, but their gain in 
hardness on quenching is less. It is clear that eutectoid steels should be 
hardened from a temperature just above Aci, that is, 750° to 800° C., for 
at this temperature the carbon, being in solution and thoroughly diffused, 
possesses its full hardening power, and the grain structure is at its finest. 
For the maximum hardness, the metal should then be quenched as suddenly 
as possible in water, by which treatment the austenite is changed into a 
fine grained martensitic or troostito-martensitic structure, depending upon 
the size of the article and other incidental conditions. In order to avoid 
the danger of cracking, many operators will prefer to quench in oil, when 
troostite may be the predominating constituent if the piece is of large size. 

Hardening Hyper=Eutectoid Steels (.90 to 1.40%): Steels that 
contain more than .90% carbon are also hardened by heating just above 




554 


THE TREATING OF STEEL 


Acs- 2 -i, or in other words, at the same temperature as steel of eutectoid 
composition, the reason for which is readily seen by a little reflection. To 
cite an example, suppose the steel to be hardened has a carbon content of 
1.30%. Such a steel in its natural state is composed approximately of 93% 
pearlite and 7% free cementite. To cause both pearlite and free cementite 
to change to austenite would require the steel to be heated above Ac cm> 
about 950°, but such a high temperature would result in a decided and un¬ 
desirable coarsening of the grain size, which is avoided by heating only 
above AC 3 - 2 - 1 . Besides, quenching from this lower temperature would 
give a harder steel than would be obtained in the first instance. For, 
supposing the quenching is such as to produce martensite, in the first case, 
the hardened steel would be composed of martensite only, whereas in the 
second instance it would be made up of 93% martensite and 7% free 
cementite, which being harder than martensite, would impart additional 
hardness to the quenched steel. When for any cause it is desirable to avoid 
the presence of any free cementite, the metal may be heated above Ac C m 
and cooled in molten lead, then reheated to slightly above Aci, and quenched 
as usual. The quenching in lead prevents the re-formation of free cementite 
and is not severe enough to cause cracking or warping, while the reheating 
to Aci accomplishes the grain refinement so much to be desired in these 
steels. 

Hardening Hypo=Eutectoid Steels (C .30 to .80%): Steel containing 
less than .30% carbon cannot be materially hardened by any of the ordinary 
commercial methods of quenching on account of the separation of ferrite 
from the solution, which takes place to some extent even with the most 
rapid methods of cooling. For hardening hypo-eutectoid steels with a 
higher carbon content, two methods may be employed. First, the metal 
may be heated slightly above Aci and quenched, when only the pearlite of 
the steel will be affected, it being changed into martensite or troostite 
according to the rate of cooling, and the free ferrite will undergo no refine¬ 
ment at all. Evidently, the second and better plan is to heat the metal 
above AC 3 - 2 , when its entire bulk changes into hardenable austenite, which 
on quenching rapidly may be converted into martensite or at least troostito- 
martensite. While this martensite, because of its lower carbon content, is 
not so hard as the martensite formed from the pearlite in the first method, 
the steel as a whole will be harder and certainly more uniform and of a 
much finer grain structure, because the original network of coarse ferrite 
will have been absorbed and refined. 


SECTION III. 

THE TEMPERING OF HARDENED STEEL. 

The Tempering Process: Tempering, sometimes spoken of as drawing- 
back or simply as drawing, consists in reheating the metal after hardening 
to some temperature below the critical ranges, and may have for its primary 





_ TEMPERING AND TOUGHENING 555 

object (1) the regulation of the hardness and brittleness of the steel, (2) 
the toughening of it, or (3) the release of the hardening strains. In 
tempering, the release of the internal stresses and strains set up by the 
hardening process is always aimed at, whatever may be the other results 
sought, for the metal is incapable of giving its best service as long as these 
or similar strains exist. This result is usually accomplished by the heating 
in the tempering process, for even heating to the temperature of boiling 
water will relieve these strains to some extent. This fact is often taken 
advantage of to relieve strains when it is not desirable to soften the steel 
to the extent that higher heating would involve. 



Legend A=Austenite, M=Martensite, T=Troostite, S—Sorbite, 
P=Pearlite. 

I. Slowly cooled. II. Quickly cooled. III. Reheating Hardened 
(Annealed) (Hardened) Steel (Tempering). 

Fig. 116. Diagram Depicting the Constituents Formed on Slowly Cooling and 

Quickly Cooling Steel and on Reheating Hardened Steel. (After Sauveur.) 

Nature and Theory of Tempering: According to the retention 
theories of hardening, which are among the most plausible ones advanced 
to accoimt for the hardening and tempering of steel, hardened steel is in 
a state of unstable equilibrium, or strain, and, therefore, is ever tending to 
assume a more stable form or condition, which tendency implies a return of 
the iron to the alpha form and of the carbon to the condition of cement 
carbon, or segregated cementite. In hardened steel, this transition is 
prevented by the rigidity of the metal, wdiich is reduced by reheating. 
The extent of this reduction of the rigidity being in proportion to the extent 
of the reheating, the higher the temperature the greater will be the extent 
of the transformation. Thus, supposing the hardening operation has 
arrested the transition of austenite at the martensitic stage, this martensite 
will begin, at a temperature some 150° C. above that of the atmosphere to 
change into troostite, and the transformation will continue with the rising 
temperature until the martensite has passed entirely into troostite, which 











































556 


THE TREATING OF STEEL 


result is no sooner accomplished than the troostite in turn begins to change 
into sorbite. When the temperature has been raised to a point near that 
of the lower critical range, sorbite, to the exclusion of other constituents, 
will predominate the structure. Any higher heating, then, carries the 
transformation into the critical ranges, where the order of transition is 
reversed, sorbite passing into troostite and then to martensite, which, as 
the temperature, on rising, emerges from the range, becomes austenite. 
The preceding diagram, Fig. 116, copied after Sauveur, will aid in under¬ 
standing these changes when they take place under different conditions. 
Evidently then, all heating for tempering is conducted below the critical 
range. By properly adjusting the temperature the transition described 
above may be arrested at any stage desired, and any combination 
of physical properties of which the steel is capable may be obtained. 
Usually the manner of cooling from the tempering temperature is im¬ 
material, and for the sake of speed or convenience quenching or air cool¬ 
ing is the general practice in heat treating shops. 

Methods of Determining Tempering Temperatures: The original 

method of estimating tempering temperatures is by color. Thus, if a piece 
of hardened steel is brightened or polished with a piece of emery, sand stone, 
or other suitable means and is then slowly heated in contact with air, the 
color of the brightened surface will, due to the formation of a surface film 
of oxide, undergo a series of color changes, called temper colors, ranging from 
faint yellow to blue, which will be characteristic of the different temper¬ 
atures reached by continued application of heat. That these colors are 
indicative of a known temperature or at least a definite condition of the 
hardened steel is generally accepted; but it is evident that the method is 
subject to the objection that differences in distinguishing different colors, 
or shades of color, is bound to occur among different operators. Distinction 
of these colors is also affected by different light conditions. The same 
temper will not give the same color in a dimly lighted room as in a well 
lighted one. While these shades are hard to describe, the color correspond¬ 
ing to the same temperature often being differently described by different 
individuals, the following table will give some idea of the colors corre¬ 
sponding to the different temperature changes. 


Table 61. Tempering Colors and Temperatures Corresponding 

to Them. 

Pale yellow.220 deg. C. Pale blue.297 deg. C. 


Straw.230 

Golden yellow.243 

Brown.255 

Brown dappled with purple. .265 

Purple. 277 

Bright blue.288 


“ Dark blue.316 “ 

“ Red in the dark.400 “ 

“ Red—indirect sunlight.525 “ 

“ Red in sunlight.580 

a Dark Red. .... 700 


U 


U 


t c 


i c 


a 
















TEMPERING 


557 


That the color method has its limitations is now well established, and 
so other methods are being developed on a more scientific basis. These 
methods involve the use of sand baths or liquid baths, such as oil, 
molten lead, or alloys, fused salts, etc., for heating the steel and the use 
of pyrometers for controlling the temperature, and aim at the elimination 
of the personal equation in the results obtained. Seeing that the tempering 
action often takes place very rapidly and that a difference of 15° or 20 & 
of temperature will often spell success or failure, such appliances would 
appear to be a very necessary part of the equipment of the modern heat 
treating shop. 

Influence of Time in Tempering: From what has been said about 
the transformations wrought in the tempering process, the reader might 
infer that the time the steel is kept at the tempering temperature would 
exert no influence. Lest such should be the case, occasion is taken to 
explain that, contrary to this inference and, in fact, to the common belief, 
maintaining the metal at the tempering temperature for a considerable 
length of time will result in producing additional tempering. This fact is 
evidenced by the change of the tempering colors at constant temperature.. 
Thus, it has been ascertained that the temper color, instead of remaining 
the same at a given temperature, advances in the tempering color scale 
as it would if the temperature were being raised, which phenomenon would 
appear to indicate that the temper colors are indicative of the tempering 
condition of the steel rather than of the temperature. For example, by 
heating a steel to 277°, where its temper color is purple, and keeping it 
there till its color is bright blue, a temper corresponding to the temperature 
288° is obtained. According to some investigators, however, the temper 
will not follow the color to the end. They maintain that each temperature 
has a maximum temper effect, which is reached quicker and quicker as 
the temper temperature is raised. 

Physical Properties Affected by Tempering: It is to be remembered 
that besides the hardness, the other physical properties of the steel are 
likewise affected by tempering. Thus, as the hardness and brittleness are 
decreased, the tensile strength and elastic limit will follow the hardness 
closely and be correspondingly decreased, while the ductility, i. e., elonga¬ 
tion and reduction in area, will be increased, though not following in the 
wake of the hardness with the same regularity as the tensile strength and 
elastic limit. (See table 62, page 561) 

Tempering the Steels of Different Structural Composition: Seeing 
that the hardening process has developed a certain structure in the steel, 
it may be well, in turning to the practical application of the principles 
and theories of tempering the hardened steels, to consider this phase of 
the subject from the standpoint of their structural composition. The 
accompanying diagram is intended to depict the tempering of all the 
hardened steels. 








558 


THE TREATING OF STEEL 


Tempering Austenitic Steels: As has already been shown, austenite 
does not occur in steels hardened by any of the commercial methods. 
Hence, a lengthy discussion of the tempering of austenitic steel is out of 
place in this study. It may be pointed out, however, that instead of passing 


Legend: A=Austenite, M=Martensite, T=Troostite, S=Sorbite. 

Fla. 117. Diagram Depicting the Tempering of Hardened Steel. (By Sauveur.) 

into martensite then to troostite, as shown at I in the diagram, austenite 
may on tempering, pass directly into troostite as indicated at II. The 
diagram shows that austenite begins to be transformed at a very low tem¬ 
perature, being completely converted into martensite at 200° C. or into 
troostite at 400° C. 

Tempering Martensitic Steels: If steel of high carbon content has 
been fully hardened by quenching rapidly, as in water, it consists mainly 
of martensite, if other conditions were at all favorable. This constituent 
is more stable than austenite, and on tempering will begin to change to 
troostite below 200° C. and this transformation is complete at about 
400° C., as shown at III on the diagram. Recalling the properties of 
troostite, it will be seen, then, that tempering between these tw'O points 
results in a material decrease of the hardness and brittleness accompanied 
by a decrease also of tensile strength and elastic limit, while some increase 
in the ductility will be noted. It is to be observed that just as martensite 
predominates in the structure of hardened steels, and pearlite, of annealed 
steels, so the presence of troostite indicates tempering, either as a separate 
reheating process or by regulating the cooling in the hardening operation, 
as for example, in oil quenching, which is often called oil tempering on this 
account. 

Tempering Troostitic Steels: Commercially hardened steels, 
especially those quenched in oil, will sometimes show large proportions 
of troostite. From the diagram it will be seen that to temper this steel 
will require a temperature of at least 400°, the temperature at which it 
begins to be changed into sorbite. At 600° C. the transformation of 




























































TOUGHENING 


559 


troostitic sorbite is complete. Tempering here results in a marked tough¬ 
ening of the steel with loss of much of the hardness. Hence, as explained 
below, tempering between these temperatures is called toughening by 
many of the heat treating experts. However, troostite steels produced 
by quenching often contain considerable martensite. When such is the 
case the steel may be softened by reheating to about 400° C., when the 
martensite will be destroyed. 

Sorbite: As this constituent occurs at the top of the tempering 
range, sorbitic steels cannot be tempered. Furthermore, as these steels 
are not produced by the regular hardening methods, they are not properly 
considered in connection with tempering. 

• 

SECTION IV. 

THE TOUGHENING OF STEEL 

Toughening is the term applied to certain treatments given usually to 
steels of medium carbon content (C. .35% to .60%) in which strength and 
toughness, rather than hardness and toughness, are the properties sought. 
It is a treatment applied to railroad axles, piston rods, and other articles 
subjected to fatigue, impact and dynamic stresses in service. As practiced 
by the Carnegie Company, toughening consists in heating the steel to 
temperatures varying from 775°C to 850°C, depending upon the chemical 
composition, quenching in oil or water, and then drawing back to such 
high temperatures, 450° to 650°C, that little, if any, of the hardness due to 
the quenching remains. 

Benefits of Toughening: Compared with annealing, toughening has 
an advantage in that both the strength and ductility of the steel may be 
increased to the limits of which the steel is capable. In annealing, strength 
is sacrificed for ductility, but in toughening, the relation of these properties 
may be nicely controlled. The effect of the quenching operation is to give 
the greatest refinement of the grain and to develop the maximum strength 
of which the steel is capable. The effect of the draw back is to relieve all 
strains due to the quenching, and, without coarsening the grain, develop 
the ductility, which will gradually increase, with a partial loss in strength, 
of course, as the temperature of the draw back is raised. Between 500° and 
600°C the draw back produces a steel composed entirely of sorbite, which 
is the structure that gives the highest combination of strength and 
ductility. The pearlite produced by the usual annealing methods is both 
less strong and less ductile than sorbite. One feature of the toughening 
operation is to increase the ratio of the elastic limit to the ultimate, 
or tensile, strength. Thus, while in natural and annealed steels of toughening 
grade this ratio is approximately 3:6, in properly toughened steel it is 
about 4:6. In view of the fact that it is the elastic limit that actually 
measures the working strength of the steel, this effect of toughening is 
worthy of careful consideration. 

Quenching for Toughening: As indicated above, either oil or water 
is used as a quenching medium for toughening. Both media have their 










560 


THE TREATING OF STEEL 





Fig. 118. Showing Change in Structure and Condition of Constituents in Steel Due 

to Heat Treatment, with the Accompanying Changes in the Physical Prop¬ 
erties. Specimens taken from large forgings, six inches in diameter, midway 
between center and outside, all from articles of the same size and design 
and forged in the same manner. (Micrographs by O. M. Ash). 


C. .49% 


Mn. 

.66% 

P. 

.020% 

a. 

.026% 


Quenched 

and 

tempered 


Heated to 
825°C and 
quenched 
in water 


Drawn back 
at 585°C 


Ladle 

Analysis 


Treatment 


Mechanical 

Properties 


Structure 


x 100. Pearlite—Large Grain Size. 


C. .48% 

Mn. .54% 
P. .020% 
S. .036% 


Annealed 

Heated 
to 830°C 
and cooled 


in air 


Ultimate 
Strength 
97,200 lbs. 


Elastic 
Limit 
62,720 lbs. 


C. .49% 

Mn. .66% 

P. .020% 
S. .026% 


as 

forged 


Ultimate 
Strength 
85,040 lbs. 


Elastic 
Limit 
44,920 lbs. 

Elongation 
in 2 " 
23% 


Reduction 
of Area 
37.8% 


x 100. Sorbitic Pearlite—Grain Size Good. 


Elongation 
in 2 " 


25 % 

Reduction 
of Area 
59.8% 


x 100. Sorbite—Grain Size Excellent 


Ultimate 
Strength 
96,370 lbs. 

Elastic 

Limit 

49,310 

Elongation 
in 2" 
20.5% 

Reduction 
of Area 
34.7% 































EFFECT OF HEAT TREATMENT 


561 


advantages and disadvantages. Water is the more rapid and drastic 
medium, and on this account, is more liable to develop cracks in the steel, 
hence some heat treaters recommend that only oil be used. On the other 
hand, a deeper penetration of the effects of the quenching and greater 
tensile strength and elastic limit are obtained with water than with oil, 
thus making it easier to meet specifications calling for high tensile proper¬ 
ties. Therefore, others will prefer water quenching under certain con¬ 
ditions. In selecting the quenching medium, it is evident that much 
depends upon the article, its shape, size, and the grade of steel it is made of, 
and much upon the skill of the operator. All these features of toughening 
are brought out in Fig. 118 and table 62. 


Table 62 Illustrating the Effect of Various Heat Treatments upon 
the Mechanical Properties of Medium Carbon Plain 
Steels. 

Chemical Composition; C. .38%, Mn. .55%, Si. .05%, P. .024%, 
S. .050%. 

Description of Pieces Treated; one inch rounds, 29 inches long; 
14 pieces, all from same billet. 

Description of Test Pieces; One test piece from each of the 14 
pieces, turned to a diameter of inch, as in Fig. 47. 


Heat Treatment 

Physical Tests 

Hardening and 

Anneal 

Tensile 

Elastic 

Elongation 

Reduction 

Brinell 

Scleros- 

Refining Deg. C 

Deg. C 

Strength 

Limit 

in 2" % 

in area % 

Number 

cope Test 

As Rolled 

• • • • 

85,000 

50,000 

30.0 

48.9 

163 

25 

Heated to 760 

° and 







cooled in f 

urnace 

74,000 

42,500 

32.0 

54.7 

134 

23 

Heated to 815° 

427° 

100,000 

67,000 

21.0 

53.9 

179 

30 

quenched in oil 

482° 

98,000 

66,000 

23.5 

52.8 

170 

29 

538° 

90,000 

59,000 

26.5 

54.7 

170 

29 


593° 

89,000 

58,000 

26.5 

63.5 

170 

29 


649° 

75,000 

53,000 

33.5 

64.7 

156 

27 


704° 

71,000 

51,000 

34.0 

59.3 

137 

25 

Heated to 815° 

427° 

110,000 

81,000 

19.0 

46.0 

223 

35 

quenched in 

482° 

103,000 

71,000 

22.5 

54.7 

192 

33 

water 

538° 

95,000 

68,500 

23.5 

61.6 

187 

32 


593° 

89,000 

63,000 

28.5 

63.0 

179 

29 


649 

82,000 

57,500 

30.5 

65.4 

156 

26 


704° 

73,000 

51,000 

34.0 

59.8 

143 

25 


iThe data for this table, as well as that for tables 65, 68, and 69, were supplied 
by Henry Wysor, of the Bethlehem Steel Company. 


































562 


TEE TREATING OF STEEL 


SECTION V. 

CASE HARDENING. 

The Process of Carburizing Iron: It is a well known fact that if 
a bar of wrought iron or soft steel be heated to a temperature close to or 
above the critical range in contact with carbonaceous materials and within a 
suitable receptacle from which air is excluded after the heating is started, 
the bar of metal will absorb carbon, the amount so absorbed depending 
upon the time the bar is kept in contact with the carbon, the temperature 
maintained during the operation, the nature of the carbonaceous material, 
and the initial composition of the bar itself. This characteristic of iron 
with respect to carbon was first made use of in the manufacture of steel 
from wrought iron by the cementation process, then for the surface car¬ 
burizing of armor plate, and finally for case hardening, or surface carburizing, 
smaller articles. Essentially, case hardening is but a special application 
of the cementation process, in which the articles treated are but partially 
carburized and the case extends but a short distance from the surface, 
leaving the central portions of the articles unchanged in chemical com¬ 
position. Thus, while the chief principle of carburizing iron has been 
known and made use of for years, it is only within recent times that case 
hardening has become a process of commercial importance. 

Application of Case Hardening: The result sought, in most cases 
where case hardening is employed, is the production of a hard, wear-resisting 
surface upon a tough, ductile core. It is, therefore, applied to many tools, 
to gears, to ball bearings and to various parts of automobiles, airplanes, 
bicycles and the like—in fact, wherever a combination of toughness and 
lightness with a wear-resisting surface is desired. On account of the wide 
application of the process and the fact that the art has not yet reached 
the stage of fullest development, a wide variation in the methods of 
applying the process is to be expected. This condition makes the subject 
a difficult one to deal with briefly and at the same time satisfactorily. 
In the following paragraphs, an attempt has been made to give a summary 
of the facts as revealed by the work of many investigators who have pub¬ 
lished or otherwise made known the results of their experiments and experi¬ 
ence. Only general features are thus dealt with, because the working out 
of details is largely a matter to be determined by experience. 

The Two Periods of the Case Hardening Process: In order to 

obtain the greatest benefits from case hardening, it is necessary that the 
carburization be succeeded by proper heat treatment, or that the carburizing 
process be considered as a part of a special heat treating process. The 
chief factors that control the carburization have already been enumerated. 
Since a relatively high temperature is employed in the carburizing process 
and the cooling, at the end of the carburizing period, is usually slow, the 
steel, as a whole, is in its softest condition, and has a large grain structure. 





CASE HARDENING 


563 


Therefore, the heat treating part of the process must combine a grain 
refining operation for low carbon steel with a hardening and grain refining 
treatment for high carbon steels. 

Kinds of Steel Suitable for Case Hardening: In general, the com¬ 
position of the steel for case hardening is limited by the desire to eliminate 
any elements that produce brittleness in the core, and also any that tend 
to retard the absorption of carbon by the steel. The elements that may 
be permitted and those that should be avoided in steel for case hardening 
will, therefore, be easily recognized after a study of the two succeeding 
chapters which are devoted to the effects of the elements upon the prop¬ 
erties of steel. For convenience, however, a list of the elements with data 
concerning their case hardening properties is given here. 

Carbon: Since the tendency of carbon, especially when present in 
any amount greater than .25 per cent., is to increase the brittleness, .30 
per cent, is the limit to which the carbon in steel for case hardening may 
rise. Therefore, the carbon content of steels for this purpose ranges from 
.08 to .25 per cent. For ordinary purposes a carbon content of .08 to .15 
per cent, is most satisfactory. However, as steel of this grade is difficult 
to machine so as to give a smooth surface, and a fairly strong core is de¬ 
sirable for some kinds of work, a carbon content of .15 to .25 per cent is 
frequently specified. Needless to say, the higher carbon grade requires 
more care in treatment than the low carbon grade. 

Manganese: While manganese increases the ability of the steel to 
absorb carbon, on account of its tendency to make the case brittle and 
sensitive to shock, the per cent, of this element is generally kept below 
.50, though steel with a manganese content of .70 per cent, is sometimes 
employed. 

Silicon: When the silicon content is raised to 2.0 per cent., the steel 
refuses to absorb carbon, hence the steel should be kept as free of this 
element as possible. The highest limit for silicon to give commercially 
satisfactory results is about .30 per cent. 

Phosphorus and Sulphur: The phosphorus and sulphur content of 
the steel should be as low as possible, not over .05 per cent, for each of 
these elements. 

Nickel: Nickel strengthens and toughens steel, but retards the car¬ 
burization of the metal. The rate of penetration’is lowered in proportion 
to the amount present, so that in a steel with a nickel content of 5 per cent., 
the rate of penetration, using solid carburizing materials, is about half 
that in the plain low carbon low manganese steels. But, offsetting this 
disadvantage, nickel steels possess certain peculiarities of structure and 
increased toughness, which make them desirable for carburizing purposes. 

Vanadium: This element also lowers the rate of carbon penetration, 
but since it is present in very small amounts, its action in this respect is 
less pronounced than in the case of nickel. 





THE TREATING OF STEEL 


r*64 


Chromium: The low carbon chrome steels, especially those con¬ 
taining about 0.5 per cent, chromium, are well adapted to case hardening, 
for the chromium not only increases the rate of penetration and the con¬ 
centration of the carbon in the case, but also materially reduces the grain 
size. Furthermore, this amount of chromium does not harden the case 
nor render it brittle beyond that which would be obtained by slightly 
increasing the carbon content of the plain carbon steel. 

The Carburizing Agent: Many investigations have been conducted 
to determine just what the carburizing action is. Originally, it was held 
that the carbon was absorbed directly at the surface of the metal and 
there dissolved, the dissolved carbon being then disseminated towards the 
interior. That dissolved carbon may move about, or diffuse, within the 
metal is accepted, but it has been proved that carbon alone in contact with 
iron has only a slight carburizing action and that, for commercial carburi¬ 
zation, the presence of carbon bearing gases is necessary. By diffusing into 
the steel where they may react with the iron, these gases act as carriers 
of the carbon. The gases available for this purpose are carbon monoxide, 
cyanogen, and gaseous hydrocarbons. Of these, carbon monoxide and 
cyanogen bearing gases are the most effective, but the former gives a much 
more uniform gradation of the carbon content from the exterior to the 
interior of the case, and is to be preferred on that account. The reaction 
by which carburization is effected with carbon monoxide is generally 
assumed to be the following: 2 C0+3Fe=Fe3C-|-C02. 

Carburizing Materials: A great number of different carburizing 
materials, consisting of gases, liquids and solids, have been tested by the 
many investigators, and of these, solids are by far the most convenient for 
the purpose as well as the most effective, when they are of the proper com¬ 
position. In the use of solid carburizers, the chief essentials to success are 
carbon in suitable form, a sufficiently high and properly regulated temper¬ 
ature maintained for a proper length of time, and reasonable care as to the 
details of preparing the carburizer and packing the articles therein. For 
supplying the carbon, many different substances may be employed, such as 
coke, wood charcoal, sugar charcoal, animal charcoal, charred bones, 
charred leather, etc. Coke and wood charcoal are not as rapid as these 
other forms of carbon. Care is required in using coke, bones, leather and 
animal charcoal to guard against imparting phosphorus and sulphur to the 
metal. The material selected should be ground or crushed to the proper 
degree of fineness and to a fairly uniform size, after which it should be 
sifted free of dust. 

Packing and the Action of Charcoal Carburizer: Assuming that 
charcoal is selected, the article or articles to be case hardened are packed 
with the carburizer in a hardening pot or box of suitable size and shape. 
The boxes may be of soft steel, wrought iron or cast iron. The walls should 
be thin, about one-fourth inch in thickness, and of a size and shape that will 




CASE HARDENING 


565 


permit the rapid penetration of the heat, so that the lag in temperature of 
the central part of the packed box behind the furnace temperature will be 
as small as possible. The best shape is one that conforms to that of the 
piece or pieces to be carburized. The article, or each of the articles, in a 
charge should be placed so that it will be completely surrounded by a 
layer of the carburizing material, about an inch in thickness. In case 
it is desired to carburize only certain parts of the article, the parts 
that are not to be carburized may be covered with asbestos cement, 
or slaked lime or fire clay in the form of a paste. When the packing has 
been completed, the open end of the box is closed with a neatly fitting 
lid, which is pressed down firmly against the top layer of carburizing 
material and fastened tightly in place, so that it will permit no displacement 
of the pack or packing in handling. The small opening about the edge of 
the lid is then luted with asbestos cement, clay, or a mixture of fire clay 
and sand; then, the box is ready for charging. When the contents of the 
box have reached a certain temperature in the furnace, the oxygen of the 
air that fills the interstitial spaces of the packing reacts with the carbon, 
giving carbon monoxide, which in turn reacts with iron to give iron carbide 
and carbon dioxide gas, as previously described. The iron carbide, of 
course, remains in the metal to form the case, while the carbon dioxide 
is given off. When it comes in contact with the carburizing material, 
CO gas is again generated, thus, CC> 2 +C =2 CO. This CO then reacts 
with iron as before. This cycle is made again and again, until the process 
is stopped, or the iron becomes saturated with carbon. In the case of bones, 
leather, and other animal or vegetable matter, other more complicated 
reactions, due to cyanogen and hydrocarbon vapors given off by these 
substances, occur in addition to the simple reactions resulting from the 
carbon, as explained in connection with the use of charcoal. 

Carburizing Mixtures and Compounds: These simple substances 
may also be used as the base materials for various carburizing mixtures 
designed to suit the conditions and the results desired. Thus, in the case 
of thin cases, where it is desired to increase the speed or rate of penetration 
and where the forming of a case of uniform thickness is essential, the follow¬ 
ing mixtures have been recommended: 

1. Powdered wood charcoal with a little heavy hydrocarbon oil added. 

2. Powdered wood charcoal, leather charcoal, and lampblack in the 
proportion of 5, 2, and 3 parts, respectively. 

3. Powdered wood charcoal, 7 parts, and animal charcoal, 3 parts. 

4. Powdered wood charcoal, charred horn and animal charcoal, in 
proportion of three parts of the first and two parts of each of the others. 

The increased rate of carburization that may be obtained by the use 
of these mixtures is due to the fact that they give off volatile hydrocarbons 
and cyanogen compounds as well as carbon monoxide, and that these com¬ 
pounds are capable of causing carburizing reactions independent of and in 
addition to that involving carbon monoxide. 




THE TREATING OF STEEL 


566 


In addition to these, mixtures of wood charcoal with common salt or 
with barium carbonate have been found very efficient and desirable car¬ 
burizing materials. Just what part common salt may play in the process 
is not known, but the action of barium carbonate is easily explained. At 
the higher carburizing temperatures it is decomposed according to the 
following reaction: BaC0 3 =Ba0+C0 2 . The C0 2 thus generated is 
immediately reduced by the hot carbon to CO gas, each volume of C0 2 
giving two volumes of CO) thus, C0 2 +C=2 CO. Jhe net effect of the 
barium carbonate, then, is to increase materially the amount of the CO 
available. By exposing the mixture, after use, to the air, the barium 
oxide takes up C0 2 , forming barium carbonate again, so that with the 
occasional addition of small amounts of charcoal the same mixture may be 
used repeatedly. Another advantage secured in using the barium carbonate- 
charcoal mixtures is that the danger of contaminating the steel with sulphur 
is entirely avoided, as these materials may be obtained practically sulphur 
free. The mixture that has been found to give the best results is one com¬ 
posed of 40 parts of the carbonate to 60 parts of charcoal by weight. 

When it is desired to obtain a thin case of high carbon content in a 
very short interval of time, quick acting mixtures are used. The sub¬ 
stances employed in these mixtures are wood charcoal, bituminous coal, 
saw dust, charred leather, prussiate of potash, sal soda and common salt. 
From these substances mixtures that will give various speeds of carburizing 
may be made. For example, a mixture of 2 parts wood charcoal, 1 part 
salt, and 3 parts saw dust is relatively slow in its action while a mixture 
of 10 parts charred leather, 2 parts prussiate of potash and 10 parts saw 
dust is characterized as very rapid. 

Heating the Carburizing Pack: For heating up the charged carbur¬ 
izing boxes, some form of gas.fired muffle furnace is preferable. The 
essential requirements of the furnace are that it must be capable of giving 
a maximum temperature of at least 1000° C., any definite temperature 
lower than 1000°, and also be capable of maintaining these definite tem¬ 
peratures uniformly throughout the heating chamber for periods of several 
days at a time. In order to avoid the rapid oxidation and consequent 
destruction of the carburizing boxes, a reducing atmosphere should be 
maintained in the heating chamber, and furnaces constructed so as to effect 
this result are most desirable. The furnace should be cold, or nearly so, 
when the packed boxes are charged, and the heating, up to the carburizing 
point, should be very gradual. The steel will thus have time to adjust 
itself to the conditions; the pack will be uniformly heated throughout, so 
that carburization will begin in all parts of the pack at the same time; 
and the evolution and generation of gases, which begins at temperatures 
slightly below 700° C., will not be too energetic. The temperature and the 
length of time for carburizing depend on the depth and the carbon content 
of the case desired, the carburizing material, and the character of the raw 





CASE HARDENING 


567 


iron or steel. In general, for a given set of materials, the higher the tem¬ 
perature and the longer the time of carburizing, the greater will be the depth 
of the carburized zone; and when solid carburizers are used, the same may 
be said with respect to the maximum carbon content or carbon concen¬ 
tration of the case. That the carburizing material may affect the speed of 
the carburization has already been intimated in discussing carburizing 
mixtures. A similar difference is also found in their action with respect to 
the concentration of the carbon. Thus, while one carburizer will give, for 
example, a case with a surface hardness corresponding to .80% carbon at 
870° C., 1.05% carbon at 900° C., etc., another will give only a .70% case 
at 870° C. and a .90% case at 900° C. In treating ordinary carbon steel, 
a temperature between 875° and 900° is considered best to avoid large grain 
size and obtain the most satisfactory results. With this temperature 
determined upon, the depth of the case and the concentration of the carbon 
may be regulated by varying the time of carburizing and the composition 
of the carburizing material employed. 

Controlling the Temperature: In regulating the temperature of the 
pack it should be kept in mind that the temperature of the furnace cannot 
be relied upon to give the actual temperature of the interior of the pack. 
The temperature of the latter, during the time it is being brought to heat, 
will tend to lag behind that of the furnace, and after a temperature of 700°C. 
is passed the chemical reactions within the pack itself may result in the 
liberation or absorption of a quantity of heat sufficient to maintain its 
temperature several degrees above or below that of the furnace. Evidently, 
then, some means of ascertaining the temperature of the interior of the pack 
is very desirable. For this purpose a pyrometer of the thermo-electric 
type is admirably suited, because with this instrument the hot junction of 
the thermo couple may be placed in the center of the pack as it is being 
made up, or inserted through a small tube so placed. 

Removal of the Articles from the Boxes After Carburizing: In 

cases where it is desired to prevent the oxidation of the surface of the 
articles treated, it is necessary either to permit them to cool nearly to 
atmospheric temperature in the boxes or to quench them by emptying the 
entire contents of the box, inverted and with its opening very close to the 
surface, into the quenching liquid. Some materials are quenched from the 
carburizing temperature for the purpose of hardening them, but in order to 
refine the grain, which is coarse, due to the long period of exposure to a 
relatively high temperature, and secure the greatest toughness combined 
with greatest hardness, the carburized articles must be subjected to special 
heat treating processes, in which case the articles may be removed from the 
carburizing boxes at any convenient time and allowed to cool in the air 
to atmospheric temperatures or at least to a temperature that gives a 
black color. 




56S 


THE TREATING OF STEEL 


Heat Treatment of Case Hardened Articles: The correct heat 
treatment of case hardened articles involves a combination of methods 
suitable to steels of different carbon content. Upon the core of low carbon 
content there is superimposed a layer of high carbon steel, which may be 
of hypo-eutectoid, eutectoid, or hyper-eutectoid composition, and the 
treatments should be varied to correspond to these three different cases 
and to the temperature at which the carburization was carried on. To 
secure maximum refinement of grain in the core it is necessary to heat the 
steel just above its AC 3 point, which for a .15% to .20% carbon core, is 
a temperature near 900°, and quench, preferably, in oil. As this temper¬ 
ature is far above the Ac range of either a hypo-eutectoid or eutectoid 
case, this treatment hardens the case but leaves its grain structure relatively 
coarse. Therefore, the article should be reheated to a temperature slightly 
above the AC 3 - 2-1 range of the case and again quenched in water or oil. 
Finally, to prevent brittleness in the case and to remove strains, it is desir¬ 
able to temper the steel at once by reheating to 200 ° or over, depending 
upon the hardness it is desired the case shall retain. The temperature 
mentioned would relieve strains but would reduce the hardness very little, 
if any. Hyper-eutectoid cases require that the treatment described above 
be modified to the extent that either the first reheating shall be above the 
Accm range, or that the article be quenched from the carburizing temper¬ 
ature, in order that the excess cementite may be retained in solution. The 
further treatment may then be a repetition of that for hypo-eutectoid cases, 
or merely a quenching from above the AC 3 - 2-1 range (750° C.). This last 
method leaves the core somewhat brittle, due to a large grain size, but 
produces a surface of exceptional wear resisting properties. In any of these 
cases, where the carburizing has been carried on at a high temperature 
and has occupied a considerable period of time, double quenchings are 
sometimes necessary to secure the best results. 

Superficial Hardening: For the most superficial hardening and at 
the same time the most rapid, such as is sometimes desirable for hardening 
certain tools, cyanide of potassium or prussiate of potassium alone may be 
used in either one of two ways. In one, the salt is melted and the article 
to be hardened is brought to the quenching temperature by immersing it 
in the fused salt, held at that temperature for a few minutes, the exact 
time depending upon the amount or extent of the carburization desired, 
and then quenched as for ordinary hardening, except that lime water should 
be used to neutralize the poisonous cyanide. In the other method, the 
article to be hardened is heated to the hardening temperature and is then 
sprinkled with the dry salt or plunged into a quantity of the dry salt. It 
is then reheated to the hardening temperature and quenched, as in the 
first method. Although often spoken of as such, this treatment is not a 
true case hardening process. 





INFLUENCE OF ELEMENTS 


569 


CHAPTER III. 

CONSTITUENT ELEMENTS OF COMMERCIAL CARBON STEEL 
AND THEIR INFLUENCE UPON ITS 
MECHANICAL PROPERTIES. 

Introductory: Needless to say that a complete discussion of the 
effects upon the properties of steel of all the elements that naturally may 
be found in it or that may be added to it would be a very lengthy one, 
indeed. Even a thorough study of the subject as limited by the title of 
this chapter would involve an immense amount of labor on the part of the 
writer and much time on the part of the reader to peruse it. The most 
that is to be expected, therefore, in the following discourse is but a brief 
summary of the opinions of the different authorities as presented in the 
various text books, the trade papers, and the reports of conventions, and 
some deductions and conclusions arrived at through personal experience. In 
examining the information from these sources, the student is confronted 
with much difference of opinion, which often results in much confusion of 
thought. But a systematic search enables the student to arrive at the 
conclusion that certain elements, like manganese, for example, are bene¬ 
ficial; others, like oxygen, are harmful; some, like phosphorus and sulphur, 
are of doubtful influence; while others may be beneficial or harmful, depend¬ 
ing upon conditions. In this regard, it is important to note that opinion 
at present is changing with respect to the influence of many of the elements. 
This is particularly true of phosphorus and sulphur, both of which were 
recently held to be injurious to steel under any conditions and at all times. 
Now, however, these elements, far from being considered as foes to good 
steel making, are, within certain limits, being looked upon as harmless to 
the steel, and even as aids for certain purposes. With these things in 
mind, an attempt has been made here to put down what appears to be the 
truth concerning these elements as revealed after a study such as that 
suggested above. 

Properties of Iron: Since iron is the element that forms the base 
material for the steel, the discussion of this subject is naturally begun 
with a consideration of the properties of this element, though pure iron is 
unknown commercially. As the physical and chemical properties of the 
element will be found under the subjects of Physics and Chemistry and 
the Heat Treatment of Carbon Steel, it is not necessary even to tabulate 
them here. In this connection, special emphasis is to be laid upon the 
strength and ductility of the element. Seeing that it is almost impossible 







570 


INFLUENCE OF ELEMENTS 


to obtain pure iron in sufficient quantity for testing, the determination of 
these properties cannot be made directly. However, figures that appear 
to be as near the true values as it is possible to get, have been assigned 
for these properties by calculating from results of pulling tests upon the 
purest forms of annealed or normalized commercial soft steels. After making 
what would appear to be a proper allowance for the influence of the small 
amounts of carbon that these steels contain, it has been established that 
pure iron has an elastic limit of about 20000 pounds, a tensile strength, or 
maximum stress, of 38000 to 40000 pounds, a reduction of area of 84%, and 
an elongation, measured in 8 inches, of 51%. From these values it is seen 
that pure iron is a very ductile substance, but weak as compared with steel. 

Effect of Carbon: The influence of carbon upon iron is so character¬ 
istic and beneficial that it is employed as the controlling element in regu¬ 
lating the physical properties of all common steels. While this element is 
capable of changing most of the physical properties of iron by uniting and 
alloying with it, its most important influence is connected with the hard¬ 
ness, strength, and ductility of the metal. Its effect upon these properties 
may be varied in extent by heat treatment, as is fully explained in the 
chapter on that subject. It is to be noted here, however, that, with respect 
to its influence upon the strength and ductility of naturally cooled steel, 
the average results obtained by four eminent investigators show that for 
each 0.1% carbon added to steel up to .90%, these properties are affected 
approximately as follows: • 

Yield point is raised.3987 pounds per sq. in. 

Maximum stress is raised.9363 “ “ “ 

Elongation is reduced.4.33% 

Reduction of area is reduced.7.27% 

Above 1.00% in carbon content, the brittleness of steel increases so 
rapidly, due to the presence of excess cementite, that its use is then limited 
to articles, relatively few in number, requiring great hardness and little 
toughness or ductility. Hence, the carbon content of commercial steel will 
seldom exceed 1.10%. 

Influence of Manganese: The chemical properties of manganese, 
which impart to it the power of combining with the oxygen of ferrous-oxide 
and of setting free the iron, make it invaluable as a cleansing, or deoxidizing 
agent, and have been referred to, time and again, in describing the various 
processes of making steel. It is here appropriate to consider the effect of 
the manganese that remains in the steel after deoxidizing. Of this residual 
manganese, it may be said that every one is agreed that its effects, when 
present up to certain limits, varying with conditions and the use to which 
the steel is to be put, are wholly beneficial. Aside from causing the steel 
to roll and forge better, it is a well known fact that manganese adds some¬ 
what to the tensile strength, this beneficial effect depending upon the 
carbon content as well as that of the manganese. According to H. H. 







MANGANESE 


571 


Campbell* the tensile strength of untreated open hearth steel, containing 
.30% manganese and over, rises for each increase of .01% in manganese 
and with the carbon content as shown in the following table: 

Table 63. The Effect of Manganese Upon the Tensile Strength of Steel. 

Each increase of .01% Mn. above .30% or .40% raises the tensile strength 
in: 


Carbon Content 

Basic Open Hearth 
(Mn. Above .30%) 

Acid Open Hearth, 
(Mn. Above .40%) 

.05 

110 lbs. 


.10 

130 “ 

80 lbs. 

.15 

150 “ 

120 “ 

.20 

170 “ 

160 “ 

.25 

190 “ 

200 “ 

.30 

210 “ 

240 “ 

.35 

230 “ 

280 “ 

.40 

250 “ 

o 

Cl 

CO 


When the manganese content is less than .30%, this law of increase is 
disturbed by other influences of an unknown character, which may even 
cause a complete reversal of tendencies and the tensile strength to rise 
when the content falls below .30%. Above 1.00%, manganese begins to 
produce undue hardness and brittleness which becomes very marked as 
the content reaches and passes 1.50%. Like the tenacity, these properties 
are similarly affected by the relation of the manganese to the carbon content. 

Influence of Manganese in Heat Treatment: Relative to heat 
treatment, the effect of manganese upon the heat treating qualities of the 
steel are not to be overlooked. In the case of ordinary open hearth steels, 
this brittleness of the high manganese steels is associated with the tendency 
of such steels to crack just before or during the quenching. Much care, 
therefore, must be exercised in selecting steel for heat treatment to secure 
the proper proportion of carbon and manganese, for which purpose the 
following statements will be found to apply in a general way: 

1 . Steels containing 1.50% manganese cannot be quenched in water, 
whatever their carbon content may be, but with the per cent, of carbon 
no higher than .60 they may, depending on the design of the body and the 
condition of the steel, be quenched in oil. 

2 . Steels containing 1.00% manganese and of low or medium carbon 
content may be quenched in water, though the risk of cracking is still great. 

3. A manganese content of .40% or less is required in high carbon 
steels near the eutectoid (.90% C.) composition, when such steels are to 
be hardened by quenching in water. 

4. In hyper-eutectoid steels, such as high carbon tool steels, the 
manganese content should not rise above .25%. 

iSee Manufacture and Properties of Iron and Steel. Published by McGraw 
Hill Book Co. 











572 


INFLUENCE OF ELEMENTS 


5. Each 0.1% of manganese lowers the critical range on heating by 
about 3° C. 

6 . According to one authority, electric steel permits a higher content 
of both the carbon and the manganese in heat treating than would be per¬ 
missible with ordinary open hearth steel. 

Influence of Manganese on Sulphur: Another great benefit to be 
gained from the use of manganese is due to its ability to neutralize, or 
offset, the evil effects of sulphur. Like oxygen, this element combines 
with both iron and manganese to form sulphides, but in the presence of 
both elements and at a high temperature it unites with the latter in pref¬ 
erence to the former, thus producing manganese sulphide, MnS, which is 
practically harmless in steel for reasons that will be explained shortly. 

Influence of Sulphur: The effect of this element upon the tenacity 
and ductility of steel, at least up to 0.1%, is so slight that it may be dis¬ 
regarded. One investigator asserts that it accelerates corrosion of the 
steel that contains it. Its most marked effects, however, are encountered 
in hot working, i. e., rolling or forging, the steel, and they were formerly 
believed to be always evil ones. That in the form of ferrous sulphide, 
FeS, it is capable of doing great harm in steel by causing redshortness is 
conceded by all, but when neutralized with manganese in sufficient amount 
it may be comparatively harmless, even when present to the extent of a 
much higher content than one-tenth per cent. 

Why Manganese Neutralizes the Effect of Sulphur: The oniy plaus¬ 
ible explanation so far offered to account for the difference in the effect of 
the two sulphides is that the iron sulphide forms films, or cell walls, about 
the grains of the metal, and as this sulphide fuses at a red heat, these cell 
walls, by becoming fluid, interrupt the continuity of the mass and so render 
the steel hot short. Manganese sulphide, instead of forming envelopes 
about the grains of the metal, collects, or segregates, into globules at tem¬ 
peratures near that of the metal on solidifying, upon which the main body 
of metal then contracts. Manganese sulphide has a much higher fusion 
point than ferrous sulphide, hence does not melt at a rolling heat, but 
becomes merely plastic like the rest of the metal. In this form, it is rolled 
into fibers, which give to the steel, when present in sufficiently large quan¬ 
tities, a fibrous structure similar to that of wrought iron. In order to 
get the full benefit of the manganese, it is necessary that it should be present 
in the steel to the extent of about three times the theoretical amount 
required for the formation of the sulphide. Roughly, this means that the 
per cent, of manganese should be five times that of the sulphur. 

Uses for Sulphur in Steel: This fibrous structure of high sulphur 
steel is made use of in the manufacture of free cutting steel, like screw 
stock, for example, because the free cutting properties of this steel are 
undoubtedly due to its fibrous structure. Thus, in this case, at least, 








SULPHUR AND PHOSPHORUS 573 


sulphur is to be regarded as a friend rather than as a foe. In this con¬ 
nection, it should be observed that experiments conducted during 1914 and 
1915 in both this coimtry and England tend to show that sulphur, when 
accompanied with a sufficient amoimt of manganese, is not such an enemy 
as it is sometimes supposed to be. Extensive investigations by our own 
research department have shown that there is practically no difference in 
the rolling, forging ©r welding qualities, nor in the physical properties, of 
steels containing from .030% to .120% sulphur. It is interesting to consider 
how the unfavorable attitude toward sulphur came about. Up to within 
the present decade, most of the steel produced in this country was made 
by the acid Bessemer process in which the sulphur content would often 
range from .070% to .100%. Yet there was no complaint about this steel, 
and that it gave excellent service for nearly all purposes that steel is used 
cannot be denied. But with the advent of basic steel, the notion became 
prevalent, through academic discussions to explain why this steel should 
be better than Bessemer, that even a small quantity of sulphur was harmful 
to the steel; and consumers, also, naturally insisted on placing the limit for 
sulphur at the lowest possible figure, under .040 per cent, or even under .030 
per cent., in order to secure the better steel. Evidently, however, such an 
attitude should be corrected now, for economic reasons, if no other. In 
view of the fact that it is becoming increasingly difficult to keep the sulphur 
content below .040%, it seems ridiculous to insist upon so low a limit, 
when the evidence points so strongly to .100% as a limit that may be made 
to serve as well, for many purposes, at least. As most basic steel made in 
this country appears to tend naturally toward a sulphur content of from 
.050% to .060%, even raising the limit to .080% would result in a great 
saving. 

Influence of Phosphorus: Phosphorus is another element that has 
been painted a little blacker, perhaps, than it should. It has been 
everywhere charged with producing cold shortness, or brittleness when 
cold, but experiments and tests conducted by our research department, 
during the first half of the year 1917, seem to indicate that up to .10% at 
least, phosphorus does not produce brittleness in the metal to a degree that 
is noticeably harmful. In these experiments, steel with phosphorus con¬ 
tents ranging from .018% to .110% were subjected to severe cold bending, 
stamping and pressing tests that steel is called upon to withstand in 
shaping, with the result that the higher phosphorus steels stood up under 
the tests as well as the low phosphorus grades, otherwise of identical com¬ 
position. That it does increase the hardness and tensile strength of the 
steel, causing at the same time a proportionate reduction in the ductility, 
is well established as a fact. In this respect it is very similar to carbon. 
Some authorities claim that it increases the tensile strength a little more 
than carbon with a less reduction in the ductility; others say that its effect 
is practically the same as carbon except that it increases the brittleness 
a little more. Campbell claims that the tensile strength of basic steel is 






574 


INFLUENCE OF ELEMENTS 


increased 1000 pounds for each increase of .01% of phosphorus. It, also, 
benefits the wearing properties of the steel in much the same way that 
carbon does. In low carbon steels, it is used in many cases with entirely 
beneficial results. Thus, it is useful in sheet bar, as it is claimed that it 
prevents the sheets from sticking together in the pack during the rolling. 

The Two Evils of Phosphorus: However, it is not to be inferred 
that the indiscriminate use of high phosphorus steel is advocated, because 
it has, according to Howe, Harbord and others, at least two evil tendencies 
that make it a dangerous element in steels for certain purposes. Speaking 
of these tendencies, Harbord states that, of all the impurities usually present 
in steel, practical experience has established the fact that phosphorus is the 
one that most prejudicially influences the physical properties of the metal 
by producing brittleness under shock, and hence for practical commercial 
purposes, phosphorus in steel should not exceed .0S0%. Again, Howe 
maintains that while phosphorus sometimes affects iron but slightly, at 
other times, under apparently similar conditions, it affects it profoundly. 
In view of this fact, which may be called the treacherousness of phosphoretic 
steel, it is difficult to define a limit for the maximum content of phosphorus 
which can be safely allowed in steel, but reasoning that the lower this is, 
the safer the material, many would insist upon a very low limit. That 
this limit may be unreasonably low is illustrated in the case of structural 
steel. Many users of this material refuse to accept any steel that contains 
a higher percentage of this element than .04%. Yet a class of material 
subjected to much more severe usage in service, namely, railroad rails made 
by the Bessemer process, is permitted to contain as much^as .110% phos¬ 
phorus. Furthermore, while structural material is subjected to static 
stresses mainly, a class of stress that phosphoretic steel is most capable 
of resisting, rails are required to withstand shocks and impacts, which 
the evidence shows, high phosphorus steels should be least capable of 
resisting. 

Influence of Silicon: Apparently owing to the fact that all but 
traces of silicon may be removed in any and all of the processes for manu¬ 
facturing steel, the attention of investigators has not been so universally 
directed to the effects of this element on steel as in the case of the other 
impurities. Besides, whatever evidence may be collected will be found to 
vary somewhat. Thus, while certain English investigators found that 
steels containing as much as 2.00% silicon, a content much higher than 
any employed in ordinary carbon steel, suffered a marked reduction in 
ductility, others maintained that the ductility is not markedly affected up 
to a content of .70%. All agreed that the tensile strength is increased, 
and some maintain that small percentages of silicon increased the resistance 
of the steel to shock. In short, it is generally accepted by all practical 
steel men that silicon up to .75% is beneficial, that it increases the yield 
point and tensile strength but does not materially impair the ductility. 




SILICON AND OXYGEN 


575 


This statement is in accord with the experience of our own Company, who 
found, for example, that in a certain specification calling for a tensile strength 
of 80,000 pounds with an elongation of 20% in eight inches, requirements 
that cannot be approached in plain untreated carbon steel, very satisfactory 
results were obtained by the addition of .50% silicon. Like manganese, 
silicon is a wonderful deoxidizer, or cleanser, of steel, and it is possible that 
the improvement in tlie quality of steel, and of basic steel in particular, 
which the addition of small quantities of the element produce, is due rather 
to this property than to any influence the residual silicon in the steel may 
have. Spring steel with the silicon ranging from .25% to .35% has greater 
resiliency than steels of lower silicon content, and without increased brittle¬ 
ness. In steel castings it is especially beneficial, as it tends to prevent 
blow holes and thus promotes soundness. In steels intended to be case 
hardened, silicon is an objectionable element, as it retards the absorption 
of carbon. Therefore, in such steels the silicon content should be low, as 
the retarding effect begins at about .04 per cent. In sheet bar, silicon is 
like phosphorus in that it tends to prevent the sheets in a pack from 
sticking together. For this purpose .06 per cent, is sufficient. 

The Influence of Oxygen in steel has been thoroughly discussed and 
emphasized in connection with the various methods for manufacturing steel. 
It may, however, again be pointed out that its effects are all evil ones, 
causing both red shortness and cold shortness in steel, and that when 
present even in so small amounts as .03% it shows a marked tendency to 
produce brittleness under shock. The amount of oxygen steel is capable 
of retaining is small. That retained even by over-blown Bessemer steel 
without deoxidizing is less than .15%. 

Combined Effect of the Elements on Tensile Strength of Steel: 

These elements, iron, carbon, manganese, sulphur, phosphorus, silicon and 
oxygen, are the ones found in all commercial grades of steel. Having 
discussed their effects separately, it may now be advantageous to consider 
their combined effect upon the metal. Of these elements only oxygen is 
to be looked upon as being always an enemy. The influence of manganese 
in steels that are not to be heat treated is always good, as is also that of 
silicon in small amounts. The tensile strength is raised by carbon, man¬ 
ganese, phosphorus, and silicon, while the ductility is decreased by carbon, 
manganese, and phosphorus. According to H. H. Campbell the influence 
of these elements varies in the different kinds of steels; and for the two 
kinds of open hearth steels in their natural state, that is, without any heat 
treatment, he sums up the combined effect of carbon, phosphorus and 
manganese on the tensile strength to be approximately as given in the 
following formulas: 

First Method (of Least Squares): 

A. Acid Steel 38600+1210 C+890 P+R=Ultimate Strength. 

B. Basic Steel 37430 -f-950 C+85 Mn+1050 P+R=Ultimate Strength. 




576 


INFLUENCE OF ELEMENTS 


Second Method (by Plotting): 

C. Acid Steel 40000+1000 C+1000 P+X Mn+R=Ultimate Strength. 

D. Basic Steel 41500+770 C+1000 P+Y Mn+R=Ultimate Strength. 

In these formulas 38600, 37430, 40000 and 41500 represents the initial 
strength of pure iron; C, P, Mn, stand for carbon, phosphorus and manganese 
expressed in hundredths of one per cent., respectively; X and Y represent 
variables changing with the carbon content as given under the heading, 
Influence of Manganese; and R is a factor that depends on the finishing 
temperature, and may be either plus or minus. 

For low carbon plain basic steel, such as that used for plates and 
structural shapes, rolled at the ordinary temperature for hot rolling, the 
following simple formula is used by many inspectors: 

T (Ultimate Strength)=39000+950 C+1050 P+85 Mn. 

The symbols in this formula have the same significance as the same 
symbols in Campbell’s formulas. 

The Influence of Copper upon the mechanical properties of steel, 
when present in small amounts, say up to .50%, is not very pronounced. 
In terms of tenths of one per cent., the effect of copper as determined by 
several different investigators is about as follows: The yield point is 
increased 1800 pounds in steels of low carbon, and 720 pounds in those of 
medium carbon content; the maximum stress, or ultimate strength, is 
increased 1200 pounds for low carbon, and 600 pounds for medium; the 
elongation is decreased .75% for low carbon, and .25% for medium; the 
reduction of area is decreased .45% for low carbon, and .50% for medium. 
From these results it is to be decided that the effect of small percentages 
of copper is slight, and what effect it has is beneficial. This declaration 
agrees, also, with the verdict of the American Society for Testing Materials. 
For years copper was looked upon as being very injurious to the steel, it 
being charged with making the steel red-short and unweldable. However, 
as early as 1899 A. L. Colby made an extensive series of investigations to 
determine what really were the effects of small percentages of copper upon 
the physical properties of the steel. Briefly, these investigations and the 
results obtained were as follows: A steel shaft 15 inches in diameter by 
fourteen feet long, corresponding in composition with the propeller shafts 
adopted by the U. S. Navy Board, but containing also .565% of copper, 
was forged without difficulty. Test specimens were doubled flat in the 
cold without showing cracks or flaws, and the tensile strength and ductility 
were well up to requirements of the Navy. In another series of tests the 
material, containing .553% copper, was forged into a gun-tube, and satisfied 
all the requirements for the U. S. Navy for a 6 inch gun. Mild steel in the 
form of ship-plates, containing .573% copper, passed all the tests required, 
except a quarter inch plate which was rolled too cold. The bending and 
quenching tests of the bars cut longitudinally were also satisfactory, but 




577 


COPPER, TIN, ARSENIC 


some, bent transversely to the direction of rolling, developed cracks. The 
material could be successfully welded, only one of the specimens tested 
breaking at the weld, and even then the breaking load was 61,630 pounds 
per square inch. Flanged cold, the material gave excellent results, and 
though most severely tested, developed neither defects nor flaws. Other 
investigations were directed to merchant bars, rails, and nickel steel all 
containing copper, and in no case was there any evidence of red-shortness, 
although the copper ranged from .089% to .486%. Colby’s conclusions 
were that a good steel may contain as much as 1% of copper without suffer¬ 
ing, provided that the sulphur content is not also high, in which case the 
metal is likely to crack in rolling. 

Even small amounts of copper in steel causes the latter to resist cor¬ 
rosion by acids much better than steels that do not contain it. The 
research department of the American Sheet and Tin Plate Company has 
shown that .15% to .25% of copper in steel sheets of heavy gauge practically 
preserves them from general corrosion, and that the resistance to corrosion 
begins to be manifested by the steel with the copper content as low as 
.03%. While copper compounds occur in many iron ores, only traces, if 
any, are to be found in the Lake Superior Ores. Hence steels made from 
these ores are practically copper free, except in cases where it is added to 
produce the non-corroding steels. Occasionally, however, whether intro¬ 
duced through accident or from the ore, steels will be found to contain 
copper to the small amount of .01% to .02%. 

Influence of Tin: While this element is not found in any of the iron 
ores, the use of detinned scrap may result in its introduction into the steel 
during the process of manufacture. Hence, the effects of small quantities 
of tin in steel are not to be overlooked, but unfortunately this matter does 
not appear to have been very thoroughly investigated. What work has 
been done shows that tin forms an alloy or a compound with iron, which 
has the property of making the steel very hard at rolling temperature. 
Thus, at one steel works it was impossible to roll a heat of steel into which 
there had accidently been introduced tin to the extent of .75%. Tin in 
steel increases the yield point and the ultimate strength of the metal, but 
to a less degree than carbon or phosphorus. So far as they have gone, 
investigations appear to indicate that .05% tin in steel would have little 
influence upon its mechanical or physical properties, but that larger quan¬ 
tities must be avoided. 

Influence of Arsenic: This element does not occur in any of the iron 
ores from the Lake Superior region, and is, therefore, never found in steels 
made from these ores. When present, however, in small amounts, unless 
special precautions are taken in making an analysis of the steel, it is reported 
as phosphorus. Small amounts of arsenic do not affect the physical prop¬ 
erties of steel; above .20% its effect is similar to that of phosphorus, causing 
cold shortness. 







578 


ALLOY STEELS 


CHAPTER IV. 

ALLOY STEELS. 

SECTION I. 

INTRODUCTORY. 

Definitions: So many different elements may occur naturally in 
steel, or be added to it, in such varying amounts with corresponding vari¬ 
ations in effects, that it is a difficult matter to determine just what con¬ 
stitutes an alloy steel even from the standpoint of chemical composition 
alone. When it is further considered that the different methods of manu¬ 
facture also exert their influence, and that certain elements may be added 
or allowed to remain for widely different reasons, the difficulty of wording 
concisely an adequate definition becomes more apparent. The definition 
adopted by the International Association for Testing Materials is as follows: 
“Alloy steel is steel which owes its distinctive properties chiefly to some 
element or elements other than carbon, or jointly to such other elements 
and carbon. Some of the alloy steels necessarily contain an important 
percentage of carbon, even as much as 1.25%. There is no agreement as 
to where the line between alloy steel and carbon steel shall be drawn.” 
In this connection it is well to note that elements other than carbon are 
always to be desired in steel of commercial grade, at least. Such elements 
may be added or permitted to remain for three distinct reasons, namely, 
(1) to correct or prevent defects that otherwise would be liable to occur 
in the final product; (2) to impart to the steel some distinctive property 
or to improve materially its natural properties; (3) to form alloys for the 
purpose of experimentation and investigation. The addition of silicon and 
manganese to steel illustrates the point it is desired to explain. In ordinary 
practice small amounts of these elements are added to deoxidize the steel, 
and incidentally the small amounts that remain in the metal may improve 
its properties. Large amounts of these elements, 1.50% to 3.50% in the 
case of silicon, and 11% to 14% in the case of manganese, may be added 
to impart properties to the steel that are distinctive and useful. Other 
proportions may be used, of course, which result in imparting properties 
that, while they are distinctive, are not useful, and so these iron alloys 
have only a scientific value. With these facts in mind, we agree with 
Henry D. Hibbard of the Bureau of Mines 1 who suggested the following 
definitions: 


iSee Manufacture and Uses of Alloy Steels. Bureau of Mines Bulletin 100. 





ALLOY STEELS 


579 


“Simple steel, which is often called carbon steel (or plain steel), 
consists chiefly of iron, carbon, and manganese. Other elements are always 
present, but are not essential to the formation of the steel, and the content 
of carbon or manganese, or both, may be very small.” 

“Alloy steel is steel that contains one or more elements other than 
carbon in sufficient proportion to modify or improve substantially and 
positively some of its useful properties.” These steels, since they contain 
a special element, are sometimes called special steels. 

“Alloy~treated steel is simple steel to which one or more alloying 
elements have been added for curative purposes, but in which the excess 
of the element or elements is not enough to make it an alloy steel.” 

4 "V # 

All the alloy steels manufactured by The Carnegie Steel Co. are made 
either in the open hearth or the electric furnace, and the alloying elements 
chiefly employed are nickel, chromium and vanadium. While a large tonnage 
of steel, containing slightly higher percentages of copper, silicon or manganese 
than that prescribed by ordinary practice for carbon steels, is made, these 
elements in such small quantities are not to be considered as alloys but 
rather as curative or intensifying elements. A definition that would agree 
with the customs of this company, then, would appear to be the following: 
An alloy steel is steel, made by the open-hearth or the electric process, 
which contains, in addition to carbon, some element or elements added 
with the object of modifying and substantially improving its mechanical 
properties in such a way as to make it more suitable for the purpose for 
which it is intended. This definition does not include the addition of 
copper for obtaining non-corrosive steel, a chemical property, nor the 
addition of small amounts of phosphorus to basic steel for she^t bar, nor 
the sulphur in screw stock, nor manganese and silicon added for curative 
purposes. 

Carnegie Types and Grades: To illustrate the importance of the 
elements mentioned above as being the ones chiefly employed in alloy 
steels, the types and grades of commercial alloy steels manufactured by 
the open-hearth process and fixed in 1919 as standards by the Carnegie 
Steel Company may be cited. They are as shown in table 64: 

These types and grades are subject to change, of course, and except 
from the standpoint of tonnage represent only a small part of the whole 
field of alloy steels. They are, however, representative of the steels made 
from the three alloying elements that, up to the present time, have been 
found to be of greatest value commercially, namely, nickel, chromium, 
and vanadium. Since it is necessary to limit the scope of this chapter in 
some way, it seems appropriate to confine it to a discussion of the influence 
of these elements upon steel and of the general characteristics of the steels 
represented by the types given in this table. 






580 


ALLOY STEELS 


Table 64. Carnegie Standard 
Nickel Steel. 


Carbon.10 to .50% 

Manganese.50 to .80 

Phosphorus not over.. .04 

Sulphur not over.045 

Nickel.3.25 to 3.75 


Open Hearth Alloy Steels. 

Low Nickel-Chrome Steel. 

Carbon.15 to .45% 

Manganese.50 to .80 

Phosphorus not over.. .04 

Sulphur not over.045 

Nickel.1.00 to 1.50 

Chromium.45 to .75 


Chrome-Vanadium Steel. 

.70 Carbon.15 to .55 

.50 Manganese.50 to .80 

Phosphorus not over.. .04 

Sulphur not over.04 

.90 Silicon not over.20 

Chromium.80 to 1.10 

/ 

Vanadium not under.. .15 

Chrome-Vanadium Spring Steel. Special Low Chrome Spring Steel. 

Carbon .45 to.55, .50to.60, .55 to.65% Carbon.80 to .95% 

Manganese.80 to 1.00 Manganese.30 to .50 

Phosphorus not over.04 Phosphorus not over. .04 

Sulphur not over.05 Sulphur not over.05 

Silicon not over.20 Silicon not over.20 

Chromium.1.00 to 1.25 Chromium.20 to .40 

Vanadium not under.15 


Chrome Steel. 


Carbon.15 to 

Manganese.25 to 

Phosphorus not over.. .04 

Sulphur not over.045 

Chromium.60 to 


SECTION II. 

NICKEL STEEL. 

Manufacture of Simple Nickel Steel: Nickel steel, said to have 
been used for the first time in 1888, may be made by any of the various 
processes for the manufacture of steel, but the greater portion is produced 
by the open-hearth process. At the steel-melting temperature nickel is 
chemically negative to iron, which is capable of reducing its oxides and 
preventing its oxidation, even when the bath is a highly oxidizing one. 
Nickel may, therefore, be added to the bath at any time practically without 
any loss or waste, but its addition is usually made just long enough before 
tapping to enable it to become properly diffused. For the same reason 
nickel cannot deoxidize iron, neither will it decompose carbon monoxide 
nor hold other gases in solution, though it is said to prevent, or hinder in 
a measure, the segregation of carbon and the other metalloids. It is not 
used, then, for a curative agent, but only for its beneficial effect upon the 
physical properties of the steel, for which purpose it is preeminently a 
strength giving element. 






























NICKEL STEELS 


581 


The Different Nickel Steels and Their General Characteristics: 

The nickel content of the useful nickel steels varies from 2% to 46%, which 
is a wider range than that covered by any other alloying element. Below 
2 % the benefits derived from its addition alone to steel are very slight 
and are not worth the extra cost. The great bulk of simple nickel steel, 
containing from two to four per cent, nickel, is used for structural purposes, 
such as bridges, gun forgings, machine parts, engines, large dynamos, steel 
rolls, and various parts of automobiles, because of the superior mechanical 
properties imparted by the metal when added in these amounts. Thus, 
for each 1% of nickel added above 2% and up to 4.00% an increase of 
approximately 6000 pounds in the tensile strength of this steel over the 
carbon steel is noted, while only a slight decrease, if any, in the ductility 
occurs, and all this improvement is secured without any heat treatment 
whatever. The best results, costs and benefits considered, appear to be 
obtained when the nickel content is between 3 and 4 per cent., the content 
aimed at for structural purposes being 3.25% to 3.50%. This steel also 
resists rusting and abrasion better than the plain carbon steels. Nickel 
steel of this grade lends itself well to heat treatment, and may also be used 
for case hardening, the only objection to its use for this purpose being the 
slight tendency of the nickel to retard the rate of penetration of the carbon. 
When the nickel content is raised above 5%, the metal becomes very hard, 
is difficult to work either hot or cold, and is rolled only by taking the greatest 
care. It is in demand where great resistance to shock is a prime quality, 
such as shield plates for protecting the ammunition of field artillery and 
the men serving the guns from rifle fire. Up to 8%, nickel increases the 
hardness of the steel to which it is added, but leaves the metal still amenable 
to heat treating. Steels containing 10% or more of nickel cannot be 
hardened by quenching, but become softer after being subjected to this 
heat treating operation. In 1914 a new alloy steel, containing 13% nickel 
and .55% carbon, was discovered by Arnold and Read. It is so hard that 
it cannot be machined or drilled, has a yield point of 134000 pounds, a 
tensile strength of 195000 pounds, and an elongation of 12% in two inches. 
Before this discovery, 15% nickel steel, tensile strength about 170000 pounds, 
was thought to be the strongest one of the series. This steel has been employed 
occasionally for shafting. Nickel steel containing 22% nickel is used when 
resistance to rusting is the prime consideration. Thus, it was employed 
in the valve stems of the salt water fire protective system installed by the 
city of New York, and in similarly exposed parts of the pumps used in the 
drainage system for the city of New Orleans. It is also said to be suitable 
for the spark poles in spark plugs for internal combustion engines. 24% 
to 32% nickel steel is used for electrical resistance, such as those employed 
in irons, toasters, and other household heaters. Nickel steels with a nickel 
content of about 24% are non-magnetic. 36% nickel steel is characterized 
by an extremely low coefficient of expansion, hence is used in balance wheels 
of watches, the pendulums of clocks, etc., in order to dispense with com- 







5S2 


ALLOY STEELS 


pensation. It is known as invar. Finally, 46% nickel steel, containing 
only .15% carbon, is known as platinite, because it has about the same 
coefficient of expansion as platinum and glass. Hence, it is employed in 
the lead wires of incandescent lamp bulbs, where formerly platinum was 
held to be indispensable. Later, a 38% nickel steel wire, coated with 
copper, was found to give better satisfaction than platinite. 

Reasons for These Peculiarities of the Nickel Steels: A study of 
the explanation offered to account for the peculiar influence of nickel upon 
steel is both interesting and instructive. Referring again to the 3.5% nickel 
steel, it is to be noted that nickel primarily influences the strength of the 
steel, and, to a less degree, the ductility. These facts are explained when 
the solubility of nickel in iron is considered. Thus, when nickel is added 
to steel, say of hypo-eutectoid composition, it dissolves in the iron to form 
an iron-nickel alloy. When this steel is cooled through the critical range, 
it is this alloy that replaces both the free ferrite and the pearlitic ferrite 
of the carbon steel. Naturally, a change in the physical properties due to 
this fact alone are to be expected. But it is in the influence of this alloy 
upon the formation of pearlite that the reason for the great increase in 
tensile strength of nickel steel is found. The separation of the cementite 
from the iron-nickel-carbon solution does not take place as readily as from 
a plain iron-carbon solution, hence the pearlite areas are larger and less 
clearly defined than in plain carbon steels. In other words, just as carbon 
and rapid cooling are obstructing agents to the transformation from 
austenite to pearlite, so also does the nickel act in a similar manner. As 
long as the nickel content is very low, not over 2 %, this influence shows 
itself only in a slight change in the physical properties as noted. These 
.changes become more marked with increase of nickel, as is to be expected, 
but the quick change in heat treating properties at 8 % or 10 % and at about 
25% are not thus accounted for. A little reflection, however, shows all 
these characteristics to be due to the same cause, namely, the retarding 
action of the nickel upon the transformation ranges. One writer represents 
this influence of nickel upon the critical points in heating as follows: 

.01% Nickel lowers the AC 3 range .235° C. 

.01% “ “ “ Ac 3.2 range .180° C. 

.01% “ “ “ Ac 2 range .087° C. 

. 01 % “ “ “ Ac! range .103° C. 

No figures are given for the Ar points, but other authorities have 

established that the Ar x point is about 80° C. below the Ac a point. In 
addition to and in connection with these facts, the effect of nickel upon 
the eutectoid ratio should also be considered. The statement that nickel 
interferes with the free formation of pearlite has already been made, and 
it now remains to be pointed out that nickel, up to about 8 %, reduces the 
eutectoid ratio below that for straight carbon steels. According to 
Bullens the eutectoid for a steel containing 3% nickel is reached when 
the carbon content is .75% and for one containing 7% nickel this value 




:ure— Degrees Centigrad 


NICKEL STEELS 


5S3 


falls to .60% carbon. All these facts, as they relate to the 3% nickel steel, 
which is the one we are most interested in, have been assembled and are 
represented in the accompanying diagram copied after Bullens, who was 
the first to represent the effects of nickel in this way. 



Fig. 119. Diagram Showing effect of Nickel Upon the Critical Ranges. 
Compared with Carbon Steel. (After Bullens, Steel and its Heat Treatment. 




















ALLOY STEELS 


584 


The preceding diagram is intended to depict the general effects of nickel 
upon the transformation ranges, which become lower and lower as the 
nickel content is increased, and the eutectoid ratio which decreases with 
increase of nickel. The diagram shows the position of the Ac and Ar points 
for carbon steel and also for steel containing 3% nickel. Thus: 

Solid line indicates the position of the ranges on cooling carbon steel. 
Dotted line indicates the position of the ranges on heating carbon steel. 
Dot and dash line indicates the position of the ranges on heating 3% nickel 
steel. 

Dash and dash line indicates approximately the position of the ranges on 
cooling 3% nickel steel. Due to a number of factors, the Arranges 
are subject to considerable variation. 

When the nickel content has been increased to 25%, these ranges are 
found to lie in a position that is entirely below atmospheric temperatures. 

Structural Changes Due to Nickel : From the preceding data a simple 
calculation will show that as the nickel, or nickel and carbon contents, are 
increased, the transformation ranges are progressively lowered until they 
reach atmospheric temperatures. This fact forms a basis for the classi¬ 
fication of the nickel steels, which are divided into the following three 
divisions: 

1. Pearlitic-Nickel Steels are those in which the nickel and carbon 
contents are such that, when slowly cooled from a high temperature, they 
will consist in whole or in par e of pearlite. In these steels the nickel ranges 
from 0 to 10% and follows inversely the percentage of carbon, which theo¬ 
retically ranges from 0. to 1.60%. 

r 

2. MartensitioNickel Steels: In these steels the nickel and carbon 
contents are high enough to lower the critical ranges to such a degree that 
only a partial transformation from austenite to pearlite occurs even on 
slow cooling. In these steels the nickel contents range from 10% to 25% 
with the carbon varying as above. 

3. Austenitic=Nickel Steels: Above 25% the influence of the nickel 
is so great that the transformation range is lowered to atmospheric tem¬ 
peratures, and the steel is always austenitic regardless of the carbon content. 
As previously pointed out, only the pearlitic steels containing about 3.50% 
nickel are of real importance commercially. 

The Constitutional Theory of Ternary Steels: In causing these 
structural changes the action of nickel is in accord with that of all the 
alloying elements. Briefly stated, the theory is that, upon the introduction 
of a third element into a given carbon steel, the steel remains at first 
pearlitic in structure, but as the content of the special element is increased 
the steel becomes martensitic, then austenitic or cementitic, depending 
upon the chemical action and alloying powers of the special element with 




NICKEL STEEL 


585 


respect to carbon and iron; and also that by keeping the amount of the 
special element constant, the same transformations may be effected by 
raising the carbon content. This statement, in so far as it relates to nickel, 
steels is expressed diagrammatically in the accompanying figure. 



Per Cent. Carbon 

Fig. 120. Constitutional Diagram for the Nickel Steels. (After Gutilet). 

This diagram shows that with a very low carbon content, say about 
.05%, the steel remains in the pearlitic condition until the nickel content 
reaches 10%, when it will be found to be in the martensitic condition. With 
a nickel content of 30% the same steel would be austenitic. But with a 
' carbon content of about .80%, for example, the steel becomes martensitic 
when the nickel content exceeds 6%, and austenitic when it reaches 16% 
or 17%. Diagrams like the preceding are useful in illustrating the effect 
of the different alloying elements and will frequently be made use of in 
the discussions to follow. 

Heat Treating Pearlitic Nickel Steels: From what has been said, it 
i should be apparent that the heat treating of nickel steel, to secure the 
| desired results, is an art that requires much experience and knowledge. 

Hence, it is only desirable to indicate what should be the proper treatment 
; for this steel, and although the heating and cooling of this steel presents 
some phenomena quite distinctive from carbon steels, it is considered that 
this object has already been attained. However, a few remarks as to how 
! the low nickel steels are benefited by heat treatment may not be out of 



















586 


ALLOY STEELS 



place. A heat treated nickel steel has a lower reduction and elongation 
than a correspondingly heat treated steel without nickel, but the increase 
in strength is much greater. Thus, for the same strength, the nickel steel 
is much tougher, and on this account nickel is much to be preferred to carbon 
for increasing tensile strength. The tensile strength and elastic limit are 
both affected by the temperature of the drawback, being decreased as this 
temperature is raised, but the reduction in area and elongation are not 
so correspondingly and gradually increased as in the plain steels. In this 
connection, a study of tables 62 and 65 will be found of value. 


Table 65: Illustrating the Effect of Various Heat Treatments upon 
the Mechanical Properties of Three Per Cent Nickel Steels. 

Chemical Composition: C. .37%, Mn. .61%, Si. .22%, P. .022%, 
S. .034%, Ni. 3.27%. 

Description of Pieces Treated: One inch rounds, 25 inches long; 
14 pieces, all from same billet. 

Description of Test Pieces: One test piece from each of the 14 
pieces, turned to a diameter of Y 2 inch, as in Fig. 47. 


HEAT TREATMENT 

PHYSICAL TEST 

Hardening and 

Anneal and 
Draw, 

Tensile 

Elastic 

Elongation 

Reduction 

Brinell 

Scleros- 

Refining, Peg. C 

Deg. C 

Strength 

Limit 

in 2" % 

in area % 

Number 

cope Test 

As Rolled 


113,000 

69,000 

22.5 

47.7 

229 

32 

Heated to 76 

0° and 







cooled in F 

urnace 

99,000 

60,000 

26.1 

48.3 

183 

26 

Heated to 

427° 

168,000 

150,000 

13.5 

47.2 

331 

48 

815° quench- 

482° 

148,000 

131,000 

18.0 

48.3 

285 

44 

ed in oil 

538° 

133,000 

118,000 

21.0 

57.3 

262 

40 


593° 

110,000 

90,000 

28.0 

64.7 

217 

33 


649° 

104,000 

70,000 

28.0 

63.0 

207 

27 


704° 

95,000 

62,500 

28.5 

51.7 

179 

26 

Heated to 

427° 

185,000 

165,000 

13.0 

51.1 

352 

50 

815° quench- 

482° 

150,000 

136,000 

17.5 

47.2 

311 

44 

ed in water 

538° 

148,000 

135,000 

16.0 

54.7 

293 

44 


593° 

133,500 

115,000 

18.5 

56.5 

269 

37 


649° 

108,000 

80,000 

27.5 

62.8 

223 - 

32 


704° 

98,000 

67,000 

28.0 

58.6 

179 

29 


* 








































CHROME STEEL 


587 


— 

SECTION III. 


CHROME STEEL. 

The Manufacture of Simple Chromium Steels is carried on by the 
open hearth, the electric, or the crucible process. At the temperature 
of molten steel, chromium is capable of reducing iron oxides, hence it is 
oxidized to a great extent in the open hearth, especially during the melting 
and boiling of the charge. All simple chrome steel is made by the addition 
of ferro-chromium to the charge. When the steel is made in crucibles, the 
ferro-chromium is added with the original charge; if in the electric furnace, 
this addition may be made at any time; but if made in the open hearth 
furnace, the ferro-chromium is added to the steel just long enough before 
casting for the alloy to be melted and become well mixed through the 
charge, as otherwise great waste of the chromium results. Chromium, 
however, is not oxidized readily enough to be of any value as a curative 
or a deoxidizing agent, and is used only for its effect as an alloying element. 
Simple chromium steels are worked by the same methods and in the same 
way as carbon steels, but unlike nickel steels, they are seldom, if ever, used 
in their natural state, heat treatment being necessary to develop the bene¬ 
ficial effects of the chromium, which is most active in responding to this 
treatment. Simple chromium steel was one of the first alloy steels to be 
made. 

Influence of Chromium: This element is preeminently a hardening 
agent in steel. Unlike nickel, which merely dissolves in iron, chromium 
forms a carbide. In steel, therefore, at least a part of the chromium will 
be in this form; but it never reacts with the carbon to the exclusion of iron, 
and in steel this carbide may exist either as iron-chromium carbide, 
xFe 3 C-yCr 3 C 2 or as a solution of Fe 3 C and Cr 3 C 2 - Thus, while nickel 
is found in the ferrite of the steel, chromium is associated with the cementite, 
and imparts what might be termed a mineral hardness to the steel. But 
the great hardness of the chrome steels is due, also, to another cause. 
This iron-chromium cementite is not as readily dissolved or diffused as 
the ordinary cementite on heating the steel through the critical range, 
nor does it segregate, or separate to form pearlite, as readily on cooling. 
This fact accounts for the peculiar changes in the critical ranges of the 
steel that the addition of small amounts of this element brings about, for 
while it tends to raise the Ac range it also lowers the Ar range. Thus, 
in quenching it helps to prevent the transformation of the austenite, and 
so adds much to the hardness in this way. From these statements it is 
to be inferred that chromium may have no hardening power when not in 
the presence of carbon. Such a conclusion agrees with the facts, as it has 
been shown by Uarbord that very low carbon chrome steels have pi ac- 
tically no hardening power. It is now, also, easily understood why the 
degree of hardness of the steel is dependent, within certain limits, upon 


% 






588 


ALLOY STEELS 


the carbon content as well as upon the chromium. An exceedingly fine 
grain structure is characteristic of heat treated chrome steels, which fine¬ 
ness of grain confers the valuable property of toughness. Thus, the net 
result from the influence of this element is to increase the tensile strength 
and elastic limit, without a noticeable loss in the ductility. One 
investigator has foimd chromium to be very efficient in retarding corrosion 
of the steel by neutral media, such as sea water, and, therefore, recommends 
its use in ship plates. 

The Microscopic Constituents of the Chrome Steels: The influence 

of chromium and carbon in determining the constitution of the steel is 
shown in the accompanying diagram. 



Per. Cent. Carbon 

Fig. 121. Constitutional Diagram for Chromium Steels. (After Guillet). 

From this diagram it is seen that, when the chromium content exceeds 
7% in steels of low carbon content or about 5% in steels of high carbon 
content, the steel is composed only of martensite, hence is very hard and 
strong, but is lacking in ductility and is inclined to be brittle. It can be 
neither hardened nor softened by heat treatment. It will be noted that 
unlike nickel, increasing the chromium content beyond a certain limit in 
a steel with a given carbon content fails to produce the austenitic condition, 
but gives a new structure made up of grains of the double carbide embedded 
in martensite. Between these two areas is a narrow range in which the 
carbide grains are somewhat less numerous than in the cementite region 
proper. This range marks the gradual transition from the martensitic to 
the cementitic condition with the gradual increase in the chromium and 
the carbon content. Like the martensitic condition, steel of cementitic 
composition is not affected by heat treatment. .For obvious reasons, then, 
to produce steels of greatest usefulness, the chromium content will be 
restricted to that required to give the pearlitic condition only. 


















CHROME STEELS 


589 


Uses of the Simple Chrome Steels: These steels are used 
wherever extreme hardness is desired. Thus, they have long been used 
for stamp shoes and dies for crushing hard ores, like some of the gold and 
silver ores. Another use is for five-ply plates for safes, where their great 
hardness is valued on account of the resistance they offer to the drilling 
tools used by burglars. Rolls for cold rolling metals are made of steel 
containing about .9% carbon and 2% chromium, while several thousand 
tons of steel containing about 1.30% carbon and .5% chromium are used 
annually for files. It is often used in steel for various special purposes, 
as for example the steel known by the name of “Crucia,” which is nothing 
more than a good grade of spring steel to which has been added from .20% 
to .40% chromium. The Carnegie Steel Company manufactures this steel 
as a part of their regular product. A type for axes and hammers, which 
contains .60% to .70% carbon and .60% to .90% chromium; another for 
chains, containing .25% to .33% carbon and .65% to .95% chromium; and 
a third for track bolts with .25% to .40% carbon and .60% to .90% chromium 
are also manufactured by this company. But the most important use for 
these steels is in the balls and rolls for bearings. For this purpose they are 
employed in low carbons for case hardening and in high carbons for heat 
treating, i. e., quenching and tempering. Of the tonnage furnished by 
Carnegie Steel Company for this purpose, that for case hardening is made 
in the open hearth, while the high carbon material is produced in the electric 
furnace. 

Heat Treatment of Simple Chrome Steel: To cite an example of the 
high grade of chrome steel: One large maker of bearings uses steel con¬ 
taining carbon, 1.10%; chromium, 1.40%; manganese, 0.35%; sulphur, 
0.025%; and phosphorus, 0.025%. Sizes smaller than one-half inch diam¬ 
eter are heat-treated by being quenched in water from 774° C. and then 
drawn to 190° C. for half an hour. For larger balls, the quenching tem¬ 
perature is 802° C. The second heating does not produce even an oxide 
color, but is enough to relieve in some degree the internal stresses due 
to the irregular cooling of quenching, so that the balls are less liable to 
crack spontaneously or to be broken in use. The strength of a good, well- 
treated ball is prodigious; a ball three-fourths of an inch in diameter, tested 
by the three-ball method, sustained a load of 52,000 pounds. On the small 
area of contact the intensity of the pressure amounts to over one million 
pounds per square inch. The Society of Automotive Engineers recommends 
less chromium than that given above, or 1 to 1.2 per cent. The critical 
ranges for these steels containing .90% carbon, vary about as follows: 

For a chromium content of .50%, from 720° C. to 745° C. 

For a chromium content of 1.50%, from 760° C. to 785° C. 

As indicating what may be expected by varying the treatment of the 
steels of this grade, the following will serve as an illustration: 







590 


ALLOY STEELS 


Table 66. Physical Properties of a Heat Treated Chrome Steel. 

Material: 1 inch rounds. 

Analysis: C., .64%; Mn., .27%; Si., .18%; Cr., 1.01%. 

Treatment: Heated to 870-871° C. Quenched in oil, and tempered as 


indicated. 


Tempering 

Temper¬ 

atures 

Tensile 

Strength 

Elastic 

Limit 

Elonga¬ 
tion in 

2 Inches 

Reduction 
in Area 

Brinnel 

Hard¬ 

ness 

400° C. 

228,000 

170,500 

5.2% 

13.7% 

478 

500° C. 

212,500 

155,500 

8.4% 

19.8% 

445 

600° C. 

186,500 

128,000 

10.3% 

22.2% 

389 


SECTION IV. 

CHROME—NICKEL STEELS. 

Influence of Chromium and Nickel When Combined: Having 

considered the effects of chromium and nickel when added separately to 
the steel, the student is interested in knowing what their combined influence 
may be. In the woids of Bullens, an impartial judge of high standing as 
an authority upon the subject of alloy steels, especially from a practical 
standpoint: “The chrome-nickel steels probably represent the best all¬ 
round alloy steels in commercial use for general purposes. Chrome-nickel 
steels of suitable composition appear to have combined in them the beneficial 
effects of both the chrome and nickel, but without the disadvantages which 
are inherent in the use of either one separately. Moreover, the presence of 
both chrome and nickel seems to intensify certain physical characteristics. 
To the increased ductility and toughness conferred by nickel on the ferrite 
there is added the mineral hardness given to the cementite and pearlite 
by the chrome, but with a greater resultant effect. Again, while the 
addition of nickel alone serves to diminish the susceptibility to brittleness 
in the steel upon prolonged heating or sudden cooling—in comparison with 
the corresponding straight carbon steels—and, on the other hand, the 
presence of chrome alone tends to the opposite effect, a suitable combination 
of the two alloying elements tends to neutralize the harmful effects and 
also to magnify the good points. This is not only brought out in the static 
strength and ductility, but also in the dynamic strength or fatigue 
resistance.” 

Types of Chrome=Nickel Steel: According to the testimony of some 
heat treating experts there appears to be a certain ratio of chrome to nickel 
which gives the most efficient combination of the physical properties. 
Thus, if the nickel and chromium are present in the right proportions, the 
lesser susceptibility of the nickel to brittleness, for example, will so modify 
the greater tendency to brittleness which is given by chrome alone, that 
a better steel is obtained than when this ratio is not observed. This ratio 
is said to be about 23^ parts of nickel to one part of chromium. Further¬ 
more, it is claimed that if the chromium content greatly exceeds this relation 

























CHROME-NICKEL STEEL 


591 


to nickel, the temperature limits are so narrowed that the successful treat¬ 
ment of the steel is made very difficult. Thus, in the three standard types 
of these steels, known as low nickel-chrome steel containing about 1.5% 
nickel, medium nickel-chrome steel with about 2.50% nickel, and high 
nickel-chrome steel, in which the nickel content rises to that of the simple 
nickel steels with 3.5% nickel, the chromium content should be approxi¬ 
mately .60%, 1.00% and 1.50%, respectively. 

Mayari Steel, termed a natural chrome-nickel steel, is made from 
certain ores found at Mayari, Cuba. These ores contain enough nickel 
and chromium to give a pig iron with 1.3% to 1.5% nickel and 2.5% to 3.0% 
chromium. When this iron is converted into steel, for which purpose the 
open hearth or the duplex, Bessemer-open hearth, processes are employed, 
practically all the nickel remains in the steel, but a large part of the chrom¬ 
ium is wasted. The steel is thus a species of low-nickel-chrome, containing 
roughly from 1.00% to 1.50% nickel and from .20% to .70% chromium. 
This steel is undoubtedly of excellent quality for certain purposes, but 
where the highest quality of chrome-nickel steel is required, most authori¬ 
ties agree that the synthetic alloy steels are superior. 

Uses of Chrome=Nickel Steels: Low chrome nickel steel is the type 
more commonly employed because of its low price and the greater ease by 
which it is machined. In static properties it is nearly equal to the higher 
nickel grades, but in resistance to dynamic stresses, shocks, etc., the latter 
are superior. Besides, since the purpose to which it is adapted is 
about the same as 3.5% simple nickel steel, low-nickel chrome is being 
substituted for this steel, also on account of the price. All three grades 
are used in automobiles, the carbon content being varied about as shown 
in the following table: 


TABLE 67: Grades and Composition of Nickel=Chrome Steels. 


Grade 

Carbon 

% 

Mn. 
Max. % 

Si. 

% 

S. 

Max. % 

P. 

Max. % 

Ni. 

'% 

Cr. 

% 

Low. 

0.20 to 0.55 

0.70 

Low 

0.050 

0.04 

1.25 

0.60 

Medium. . 

.20 to .55 

.70 

Low 

.050 

.04 

1.75 

1.10 

High. 

.20 to .55 

.70 

Low 

.050 

.04 

3.50 

1.50 


An important use of these steels is in armor plate. Thick armor is 
face hardened by a carbonizing process, but the body has the original 
composition, which is approximately as follows: C., .33%; Mn., .32%; 
S., .03%; P., .014%; Si., .06%; Ni., 4.00%; and Cr., 2.00%. Medium armor, 
three to five inches in thickness, is not face hardened, but is given high 
properties throughout by the proper heat treatment. The composition of 

























592 


ALLOY STEELS 


this armor is approximately, C., .30%; Mn., .34%; S., .03%; P., .03%; 
Si., .13%; Ni., 3.66%, and Cr., 1.45%. The nickel chromium steels are 
used in the manufacture of most armor piercing projectiles, also. 

Heat Treatment of Chrome=Nickel Steels: The heat treatment of 
these steels is about the same in kind and method as that for simple nickel 
and chrome steels, and is varied to suit the kind of material and the purpose 
for which the steel is to be used. To give a general idea of the proper 
treatment for these steels, the recommendations of Bullens may be cited: 

I. “For forgings: 

a. Quench in oil from about 175° to 200° F. (97° to 110°C.) over 
the critical range. 

b. Quench in oil from about 50°F (28°C) over the critical range. 

c. Anneal at about 75°F (42°C) under the critical range and 
machine. 

d. Quench in the proper medium from about 50°F (28°C) over the 
range. 

e. Draw the temper to suit the work in hand.” 

II. “For shafts and other structural parts in which the desired physical 

properties may be obtained by a drawing temperature of about 
900°F (500° C.) or over, and which will leave the steel in a 
machinable condition, treatment I. may be modified at (c) as thus 
noted, and no further treatment will be required. 

a. Quench in oil from about 175° to 200° F (97° to 110°C) over 
the critical range. 

b. Quench in oil from about 50°F (28°C) over the critical range. 

c. Draw at 900 °F (482 °C) or more, as the work may require. 
Machine.” 

III. “The full treatment as given under (I) may be modified, if desired 

to the following, for parts to be drawn below 900° or 1000° F. 
(482° or 540°C.) 

a. Quench in oil from about 175° to 200° (97 to 110°C) over the 
critical range. 

b. Reheat to about 25° to 50° F. (14° to 28 °C) over the critical 

range and cool slowly. Machine. 

c. Quench in oil from about 50° (28°C) over the critical range. 

d. Draw to the temperature required by the work.” 








ALLOY STEELS 


593 


The data supplied in tables 68 and 69 will serve as a basis for comparing 
the mechanical properties of the chrome-nickel steels, both in their natural 
and heat-treated states 

Table 68: Illustrating the Effect of Various Heat Treatments upon the 
Mechanical Properties of Low=Chrome=Nickel Steels. 

Chemical Composition: C. .39%, Mn. .52%, Si. .18%, P. .017%, 
S. .042%, Ni. 1.18%, Cr. .58%. 

Description of Pieces Treated; One inch rounds, 25 inches long; 
14 pieces, all from same billet. 

Description of Test Pieces; One test piece from each of the 14 
pieces, turned to a diameter of ]/% inch, as in Fig. 47. 


HEAT TREATMENT 


PHYSICAL TESTS 


Hardening and 
Refining Deg. C 

Anneal and 
Draw, 
Deg. C 

Tensile 

Strength 

Elastic 

Limit 

Elongation 
in 2"% 

Reduction 
in area% 

Brinell 

Number 

Scleros- 

copeTest 

As Rolled 

.... 

99,000 

59,000 

25.5 

54.4 

208 

29 

Heated to 

760° and 

89,000 

54,000 

30.0 

56.5 

170 

25 

cooled in F 

urnace 







Heated to 

427° 

139,000 

114,000 

15.5 

51.4 

331 

42 

845° quench- 

482° 

130,000 

113,000 

15.0 

53.9 

321 

44 

ed in oil 

538° 

113,000 

88,000 

17.5 

59.8 

255 

34 


593° 

113,000 

86,000 

21.0 

62.8 

229 

32 


649° 

108,000 

81,000 

25.0 

64.7 

229 

31 


704° 

97,000 

70,000 

27.0 

67.7 

207 

29 

Heated to 

427° 

174,000 

158,000 

14.0 

47.2 

363 

46 

845° quench- 

482° 

150,000 

135,000 

16.5 

45.7 

221 

44 

ed in water 

538° 

140,000 

125,000 

20.0 

55.2 

285 

44 


593° 

124,000 

108,000 

22.0 

60.8 

255 

40 


649° 

110,000 

91,000 

26.0 

66.0 

229 

33 


704° 

90,000 

70,000 

34.0 

69.2 

187 

25 












































594 


ALLOY STEELS 


Table 69: Illustrating the Effect of Various Heat Treatments upon the 
Mechanical Properties of High=Chrome=Nickel Steel. 

Chemical Composition; C. .34%, Mn. .64%, Si. .20%, P. .010%, 
S. .036%, Ni. 3.65%, Cr. 1.24%. 

Description of Pieces Treated; One inch rounds, 25 inches long; 
14 pieces, all from same billet. 

Description of Test Pieces; One test piece from each of the 14 
pieces, turned to a diameter of y inch, as in Fig. 47. 


HEAT TREATMENT 


PHYSICAL TESTS 


Hardening and 
Refining Leg. C 

Anneal and 
Draw, 
Deg. C. 

Tensile 

Strength 

Elastic 

Limit 

Elongation 
in 2" % 

Reduction 
in area % 

Brinell 

Number 

Scleros- 
cope Test 

As Rolled 

.... 

172,500 

138,000 

11.5 

26.5 

444 

57 

Heated to 76 

0° and 

125,000 

78,000 

18.0 

47.2 

255 

38 

cooled in F 

urnace 







Heated to 

427° 

190,000 

166,000 

12.5 

50.0 

415 

55 

845° quench- 

482° 

170.000 

154,000 

15.0 

44.3 

341 

41 

ed in oil 

538° 

142,000 

126,000 

20.0 

57.8 

321 

43 


593° 

127,500 

115,000 

22.0 

62.3 

285 

36 


649° 

117,000 

99,000 

23.0 

64.7 

255 

37 


704° 

115,000 

69,000 

24.0 

56.0 

255 

35 

Heated to 

427° 

164,000 

152,000 

17.5 

56.0 

375 

51 

845° quench- 

482° 

160,000 

147,500 

15.5 

53.9 

341 

48 

ed in water 

538° 

145,000 

130,000 

21.0 

58.6 

321 

43 


593° 

124,000 

100,000 

22.5 

62.8 

269 

40 


649° 

120,000 

99,000 

24.0 

63.7 

248 

36 


704° 

120,000 

69,000 

17.0 

50.0 

269 

36 










































VANADIUM STEEL 


595 


SECTION V. 

VANADIUM STEELS. 

Simple Vanadium Steels do not at present have the standing they 
formerly had, and the only reason for mentioning them here is to enable 
the reader to get an idea of the effects of vanadium alone, so that he can 
better understand the reasons for chrome vanadium steel, to be considered 
later. Since 1917 the Carnegie Steel Company has manufactured but 
one grade of vanadium steel, known as type <4 F,” which is used as a flux 
in oxyacetylene, oxyhydrogen, and electric welding. 

Influence of Vanadium: Unlike nickel and chromium, vanadium is 
an intense deoxidizing agent, being capable of carrying the cleansing of the 
steel beyond the point obtainable by manganese, or even silicon and 
aluminum. Thus, this element performs the double function of a curative 
and an alloying element. It is added to the steel, in the form of ferro- 
vanadium, containing about 35% of the element, at the time of tapping, if 
the steel is being made by the open hearth process, and preferably after 
the other ladle additions to avoid undue wastage. Of the vanadium that 
is retained by the steel, only very small amounts, from .15% to .25%, are 
required to affect the physical properties of the steel. Like most of the 
alloying elements, it tends to give a finer and denser structure than that 
of carbon steel, and for the most part its action is similar to other alloying 
elements. But in some respects, at least, it presents characteristic 
phenomena. Thus, there are good reasons to believe that, when present 
even in the small amounts noted above, it is both dissolved in the ferrite, 
like nickel, and exists as a carbide or a double carbide in the cementite, 
like chromium. It has a powerful influence upon the transformation ranges, 
as is seen from the fact that while steels containing .2% carbon and .7% 
vanadium, or .8% carbon and .5% vanadium, are pearlitic, any increase 
of the vanadium content over these limits renders the steel cementitic as 
shown in the following diagram: 



Per Cent. Carbon 

Fia. 122. Constitutional Diagram for Vanadium Steels. (After Guillet). 

As revealed by the static physical tests, the benefits from vanadium 
are somewhat similar to those for the pearlitic nickel steels, that is, it 
gives a combination of high elastic limit and ductility. With proper heat 
treatment, it is also said to resist shock, alternate stresses, wear 
and fatigue. 











596 


ALLOY STEELS 


SECTION VI. 

CHROME-VANADIUM STEELS. 

Effect of Combining Chromium and Vanadium: In order that the 

influence of vanadium as indicated above may be realized to the fullest, 
the presence of another element as an intensifier is required. Just as 
chromium intensifies the influence of nickel, so does it also stimulate 
vanadium, but to a much greater degree, it is said, than with the former. 
Hence, though various combinations have been tried, such as vanadium- 
nickel, chrome-vanadium-nickel, etc., the tendency at present points to 
the general adoption of the one combination, chrome-vanadium. 

Properties and Uses of Chrome=Vanadium Steels: The hot working 

of these steels presents no difficulties, the steel behaving in the press and 
rolls much like the higher carbon plain steels. In physical properties, they 
are similar to chrome-nickel steel except that their contraction of area 
for a given elastic limit is a little greater. They are also said to be more 
easily machined than chrome nickel steel and are more free from surface 
defects, such as scale-pits and seams. While some enthusiasts maintain 
that it is the steel best adapted to resist shock and fatigue, others hold 
that the chrome-nickel steel answers all requirements just as well. Perhaps 
the truth of the matter is that, while both steels are available for most 
purposes, there are limited fields in which one may excel the other and in 
which each has its own sphere of usefulness. Most of the chrome-vanadium 
steel made by the Carnegie Steel Company is used for driving axles and 
other forgings for locomotives, automobile springs and axles, compressed 
air flasks, torpedo tubes, and gup forgings. They are nearly always heat 
treated before being put into service, but in some automobiles the frames, 
and even part of the forgings and shafts, are made of the steel in its natural 
state. The composition and properties of three grades of this steel in the 
untreated condition are given herewith. 


Table 70. The Composition and Mechanical Properties of 
Untreated Chrome=Vanadium Steels. 


COMPOSITION 


TENSILE PROPERTIES 


Grade 

No. 

C. 

% 

Mn. 

% 

Si. 

% 

S. 

% 

P. 

% 

V. 

% 

Cr. 

% 

Tensile 

Strength, 

Pounds 

Elastic 

Limit, 

Pounds 

Contra¬ 
ction of 
Area, % 

Elonga¬ 
tion in 2 
Inches% 

1 

0.57 

0.84 

0.27 

0.04 

0.01 

0.31 

1.36 

142,000 

114,000 

42 

14 

2 

.46 

.48 

.20 

.03 

.01 

.14 

1.17 

125,000 

95,000 

55 

20 

3 

.18 

.32 

.18 

.03 

.01 

.20 

.74 

65,000 

47,200 

62 

23 


Some idea of the general results obtained from heat treating the chrome 
vanadium steels and of the methods employed may be gained from the 
following table: 








































CHROME-VANADIUM STEEL 


597 


Table 71. Physical Properties of Treated Chrome=Vanadium Steels. 
Tests made on Small Rolled Sections 


CHEMICAL COMPOSITION 

HEAT 

MINIMUM PHYSICAL RESULTS AFTER 

TREATMENT 


TREATMENT 


Carbon 
Per Cent. 

Manga¬ 

nese, 

Per Cent. 

Chrome- 

ium, 

Per Cent. 

V ana-, 
dium, 
PerCent. 

Water 
Quenched, 
Deg. C. 

Draw 
Deg. C. 

Tensile 
Strength, 
Lbs. per 

Sq. In. 

Elastic Limit, 
Lbs. per 

So. In. 

Elogation 

in 2 in. 

Per Cent. 

Reduction 

of Area, 

Per Cent. 

* .19 

.49 

.96 

.23 

850. 

749 

101,400 

91,200 

27 

69 

... 


... 

... 


712 

109,500 

98,800 

24 

66 



... 

... 


675 

121,200 

113,100 

22 

66 



... 

... 


635 

129,600 

121,200 

21 

60 






596 

136,000 

125,700 

20 

60 

• • • 





574 

146,900 

137,200 

20 

58 

* .25 

.30 

.85 

.14 

850. 

748 

88,640 

78,960 

29 

77 





.... 

697 

98,520 

92,200 

26 

72 






657 

118,700 

114,100 

24 

72 






607 

121,800 

118,200 

22 

69 

. . . 





574 

132,400 

125,800 

20 

64 

f-38 

.41 

.97 

.24 

815 

704 

100,000 

88,000 

27 

65 





649 

118,000 

101,000 

23 

60 






593 

130,000 

108,000 

18 

52 






538 

130,000 

108,000 

16 

50 






482 

157,500 

142,000 

15 

47 





Oil 

Quenched 

427 

177,500 

155,000 

11 

36 





815 

700 

95,000 

75,000 

30 

65 






650 

117,000 

98,000 

20 

57 






595 

125,000 

105,000 

18 

56 






540 

133,000 

113,000 

18 

50 






480 

143,000 

116,000 

16 

48 

... 

. . . 

. . . 

. . . 


430 

149,000 

120,000 

15 

49 



. . . 

. . . 

Annealed 

760 

88,500 

58,000 

30 

59 

* 

> 



As Rolled 


127,500 

96,500 

20 

48 

» 


♦Silicon .05%. Phosphorus under .035%. Sulphur under .04%. 
fSilicon .25%. Phosphorus .021%. Sulphur .041%. Tests on 1" rounds. 


























































































WORD INDEX 


Abrasion tests..- 

Abramsen straightening machine 

Absolute temperature. 

Absorption. 

Acetanilide. 

Acetylene. 

Acid. 

Acid anhydride. 

Acid Bessemer iron. 


Acid Bessemer process. 

Acid Bessemer steel. 

Acid Flux. 

Acid lining in converter 
“ “ in open hearth. 

Acid refractory.... A . 

Acid slag. 

Adamite rolls. 

Adhesion. 

Afterblow. 

Air chamber in open hearth 

Air cooling. 

Air port. 

Alkalies. . 

Alligator Shears. 

Allotrimorphic crystals.... 

Allotropy. 

Alloy. 

Alloy steel. 

Alloy steel ingots. 

Alloy treated steel. 

Alpha iron. 

Alternating current. 

Alternator. 

Alumina. 

in ores. 

“ in slags. 

Aluminum. 

Ammonia. 

Ammonia gas. 

Ammonia liquor. 

Ammonium sulphate. 

Amorphous carbon. 

Ampere. 

Angles. 

Angular fracture. 

Angular method of rolling.. 

Anhydride. 

Aniline. 

Aniline hydrochloride. 

“ salt. 


35 

468 

7 
5 

109 

69 

.... 8-15 

15 
129 
40 

..172 to 194 
187 
118 
184 
200 
29 
123 
323 
4 

200 

216 

....211-542 

213 

39 

473 

533 

.23-528-532 

8 
579 
362 
579 
532 
251 

246-247-253 

.... 26-39 

. .39-41-160 
118 

..11-26-166 

.... 25-116 

....100-116 

.... 99-116 
116 
23 

....245-262 

462 

306 

446 

.... 15-16 

109 
109 
109 


Annealing steel. 539 

“ box. 546 

oven (furnace).459-546 

temperatures.540-541 

Anthracin oils. 115 

Anthracite coal.66-78-190-228 

Anthranilic acid... 113 

Antifriction metal (see bearing metals)... 331 

Antimony. 12 

Anti pyrin. 115 

Arc, electric. 264 

Arc, furnace.261-265 

Archean era. 79 

Armor plate. 591 

Arsenic. 12 

“ in blast furnace. 16fr 

Ash in coal.75-76-80 

“ in coke. 85-160 

Aspirin. 115 

Atomic weights. 11-12 

Atoms. 10 

Austenite. 526 ; 

Austenitic nickel steel. 584 

Available base. 118 

Avogadro’s hypothesis. 13 

Axles, manufacture of.508 to 515 

Azo benzene. 109 


Ball stuff. 184 

Banking. 159 

Bank ovens.. 87 

Barium. 11 

Barium carbonate in case hardening. 565 

Bar mill. 474 

Base, chemical. 8 

Base of rail. 449 

Basic anhydride. 15 

“ Bessemer process. 172 

“ flux. 118 

“ open hearth process. 198 

“ ore. 40 

“ pig iron. 129 

“ process. 175 

“ refractories. 30 

“ slag. 123 

Battery of coke ovens. 86 

Bauxite. 31-32 

“ brick. 32 

Beams. 465 

Bearing metal. 331 










































































































600 


WORD INDEX 


Beehive coke. 

“ coke oven. 

“ process. 

Belgian mill. 

“ oven. 

Bell and hopper. 

Belly pipe. 

Bending test. 

Benzaldehyde. 

Benzene. 

Benzene series. 

“ sulphonic acid. 

Benzenyl trichloride. 

Benzidine. 

Benzine. 

Benzol. 

“ manufacture of. 

grades of. 

“ uses of. 

Benzoic acid. 

Bertrand-Thiel process. 

Bessemer converter, construction of 
“ Henry. 


iron. 

“ steel.. 

steel process.... 
" (steel) converter 

“ reactions in. 


Beta iron. 

Billet. 

“ mill. 

Binary compounds. 

Binder in coal. 

Binding material for refractories 

Birmingham ore district. 

Bituminous coal. 

Blanks for wheels. 

Blast for Bessemer converters.. 

“ for blast furnace. 

*' for cupola. 

“ furnace, construction of. . 
“ . “ equipment of. . . 

“ foundation of_ 


Bleeder. 

Blind pass__ 

Blister. 

Block of ovens. 

Bloom. 

Blooming mill. 

Blow. 

Blower. 

Blowing engine 
Blow holes.... 


....86 to 90 

. 86 

. 86 

. 477 

. 90 

. 139 

. 134 

. 308 

. 112 

69-105 to 110 

. 69-106 

. 110 

..... 112 

.108-109 

. 69 

..101 to 110 
... 100 to 105 

. 107 

.107-109 

. 112 

. 201 

. 183 

. 176 

. 40 

. 129 

. 190 

. 175 

.. .183 to 186 
... 193 to 196 

. 532 

. 365 

...391 to 406 

. , 18 

. 80 

.29-30-31 

. 42 

.66-78-80 

.497-505 

. 180 

. 150 

. 179 

. 131 

. 130 

. 131 

. 66-71 

. 141 

. 426 

. 435 

.87 

. 365 

...366 to 384 

. 187 

. 188 

.150-180 

. 346 


Blow in. 152 

Blow off valve.143-156 

Blowing in burden. 153 

Blowpipe. ' 134 

Body of rolls. 322 

Boil in a converter. 188 

“ “ “ open hearth. 221 

Bone coal. 80 

Boron. 12 

Bosh. 135 

“ bands. 135 

“ brick. 137 

“ plates. 136 

“ plate boxes. 136 

Bott. 134 

Bottom blown converter. 183 

“ casting.229-324 

“ of blast furnace. 132 

“ of converter. r. 185 

“ of open hearth. 219 

“ pouring. 228 

“ stuff. 185 

Box annealing. 546 

Box pass. 323 

Boyles’ law (see volume of a gas). 2 

Braddock insulated rail joints. 454 

Braddock works (see Edgar Thomson)_177-183 

Brasses. 331 

Breaking load. 304 

Breakout in open hearth.:. 230 

Breeze, coke. 90 

Brick, silica. 29 

“ clay. 30 

“ hearth and bosh.137-138 

“ in-wall. 137-138 

“ top.137-138 

Bridgewall. 211 

Brightman straightener. 468 

Brine for hardening.551-552 

Brinell tests.310-311 

“ hardness number.310-311 

Briquettes (or Briquets).66-220-242 

British thermal unit. 7-60 

Bronze. .. 331 

Brookville coal bed. 79 

Brown coal. 77 

Brown ore. 36-37 

B. T. U or B. t. u. 7-60 

Buckles in plates.426-435 

“ in bars. ; . 494 

Bucket hoist.. 140 

Buggy for Bessemer plant. 182 

“ for open hearth. 207 

Bulkhead. 211 

Bullens. 517 

Bull head rail. 437 
































































































































WORD INDEX 


601 


Bundling merchant bars. 491 

for export. 491 

Burdening blast furnace. 159 

Burden on a blast furnace. 159 

Burned steel. . 495 

Bustle pipe. 135 

Butane.... 70 

Butterfly method of rolling. 462-463 

By-pass. 150 

By-product coke.85-90 to 98 

gas (Cokeoven Gas) . 66-71 

plant. 98 

process. 90 

' “ advantages of. 91 


Cadmium. 11 

Calcination of dolomite. 25 

“ limestone. 25 

“ magnesite...:. 25-231 

Calcined dolomite... 32 

magnesite. 32 

Calcining plant. 202 

Calcite (see limestone). 36 

Calcium.r. 11-25 

“ carbide in electric furnace slag . .122-228 

Calcium carbonate. 25-166 

fhiroide(seeFluorspar)120-223-268-270-282 

oxide. 25 

silicates. 123 

sulphate... 237 

“ sulphide..270-287 

Caliper. 503 

Calorie. 7 

Calorific power. 60-61 

intensity. 60-63 

Calorimeter. 62-63 

Camber in rails. 450 

Campbell furnace. 200 

“ H. H. 570 

process. 201 

Carbolic acid. 115 

Carbon. 23 

compounds. 24 

“ dioxide in Bessemer process. 194 

“ in blast furnace.163-167 

“ in O. H. process. 238 

“ in producer gas. 72 

“ in blast furnace. 163 

" iron diagram.524-529 

“ monoxide. 22 

in Bessemer process. 194 

“ “ blastfurnace. 167 

“ case hardening. 564 

“ electric furnace. 286 

.O. H. process. 238 

“ “ “ producer gas. 72 


Carbon monoxide in steel.269-518 

steel (see plain steel). 579 

in pig iron. 127 

“ “ combined. 127 

“ “ “ “ graphitic. 127 

steel. 570 

steel for case hardening. 563 

Carbonizing agent. 564 

box. 564 

materials. 564 

mixtures... 565 

pack. 566 

Carbonless i ron. 518 

Car dumper. 151 

Carnegie Schoen wheels. 497 to 506 

“ tape size. 504 

Case. 567 

“ hardening. 562-568 

Casting iron. 172 

“ machine. 152 

“ steel. 312 

Castors. 429 

Catcher.;. 475 

Cellulose... „. 77 

Cement carbon. 533 

Cementation process.173-562 

Cementite in pig iron. 127 

“ “ steel. 518 

Cenozoic era. 79 

Centering for axles. 511 

Centigrade. 6-7 

Channels.463-464 

Charcoal. 66 

“ iron. 324 

Charging blast furnace. 156 

boxes. 207 

machine. 208 

Chemical calculations. 19 

change. 8-9 

compound. 8 

equations. 13 

formulas. 13 

nomenclature. 18 

radicals. 14 

reactions, laws of... 17 

symbols. 9 

Chemistry. 3 

Chill, depth of. 325 

“ test. 155 

Chilled hearth. 158 

“ iron.324-326 

“ roll. 324 

Chimneying. 158 

Chimney valve.— 143 

Chlorine. 11 

Chocks.322-331 
























































































































602 


WORD INDEX 




Chromite. 

Chrome brick. 

“ nickel steel 


“ steel. 

“ vanadium steel. 

Chromium. 

in blast furnace. 

“ steel for case hardening 

Cinder. 

“ cooler. 

“ notch. 

“ pitman. 

Circular mil. 

Circular shapes. 

Clairton coke plant. 

Clarion coal bed... 

Clay. 

“ fire. 

“ flint. 

“ plastic. 

“ brick. 


Cleaning plant for blast furnace gas 

Cleavage.. 

“ planes. 

Clinton iron ore. 

Closed pass... 

Coal, kinds of. 


Cobalt. 

Cobble. 

Cogging mill. 

Cohesion. 

Coil, of hoop. 

Coke. 

“ breeze. 

oven Gas 
Coking process 

Colby. 

Cold bend tests.... 

“ blast. 

“ short. 

“ templet. 

“ blast valve... 

“ working. 

Collar marks.. 

Collars on axles 
“ “rolls.... 
Combination mill. . 
Combination plate. 
Combined carbon.. 

water... 
Combining weights 

Combustion. 

Compression tests. 


26-31-32-231 

. 31 

. 590 

. 231 

. 587 

. 595 

. 26 

...... 166 

. 564 

. 120 

. 134 

. 134 

. 218 

. 257 

..497 to 507 

. 93 

. 79 

. 29 

. 29 

.29-138 

. 29-138 

. 30 

. 146 

. 533 

. 533 

. 79 

. 323 

. 66 

. 66-71 

. 66-67 

. 11 

. 414 

. 365 

. 4 

. 473 

. 66-80-85-160 

. 90-98 

_ 66-71 

. 88 

.263-576 

. 308 

. 150 

. 233 

. 439 

. 143 

.313459 

. 414 

. 512 

. 323 

.330477 

. 427 

. 127 

. 1541 

. 9-10 

. 60 

. 33 


Concentric converter. 183 

Conduction of electricity. 244-256 

“ “ heat...*. 59 

Conductors of electricity. 245 

Confining die. 460 

Congo red. 114 

Coning of wheels. 504 

Constitutional diagram.585-588-595 

Continuous coil. 473 

furnace. 421 

“ mill.397 to 405 

Contraction of area (see reduction of area) 307 

of ingots. 343 

“ tests. 34 

Convection of heat. 59 

Converter.183-186 

“ reactions.193-197 

Cooling bed. 479 

“ for annealing. 543 

“ hardening. 551 

“ “ tempering. 557 

Cope. 324 

Copper. 12 

“ bearing steel. 576 

“ effects on steel. 576 

“ in blast furnace .•. 166 

“ in bearing metal. 331 

Corrosion of steel. 577 

Cort, Henry. 318 

Cotton seed oil. 553 

Cotton tie.472496 

Coulomb. 245 

Coupling box.318-322-330-334 

Covington drawing machine. 90 

Cracks in billets and blooms. 417 

“ “ ingots. 349 

Cresole. 115 

Critical points. 527 

“ range. 527 

Cross country mill.330479 

Crucible of blast furnace. 132 

“ steel. 174 

Crude still. 102 

Cryohydrate. 522 

Crystals. 533 

Crystallization. 5-348 

of steel. 533 

water of. 15 

Cup and cone. 139 

Cupola. 179 

“ charge.,...178-204 

Cupped fracture.. ... 306 

Cutting axles. 511 

“ rails. 450 

“ shapes.466*468 

Cuyuna ore range. 47 




























































































































WORD INDEX 


603 


Dalton. 10 

Debenzolating tower. 100 

Decalescence. 527 

Decane. 70 

Deep seated blow holes. 346 

Defects in semi-finished material.413 to 417 

Definite proportions, law of.. 9 

Deformed bars. 469 

Deliquescent substance. 16 

Delta connections. 255 

Dendrite. 533 

Density. 4-34 

Deoxidation of Bessemer steel.190-197 

in electric furnace.269-286 

Dephosphorizing slag. 270 

Destructive distillation. 85 

Desulphurizing.269-286 

Detinned scrap. 577 

Diagonal method of rolling.447-465 

Diamond, form of carbon. 23 

pass. 323 

Di-basicacid. 19 

Die for punching rail joints. 459 

Differential hardening. 553 

Diffusion. 5 

Dilation of steel. 530 

Dimethylaniline. 112 

Diphenylamine. 112 

Direct current. 253 

“ process, Siemens. 199 

Discard.343-498-509 

Divided circuit. 258 

Dolomite.26-31-32-119-230 

Double acting hammer. 315 

“ annealing. 546 

“ bell and hopper. 139 

Downcomer. 141 

“ take. 141 

Drag-over mill. 330 

Draught.339-381 

Drawing coke. 89 

Dressing rolls. 329 

Drill tests for ore. 47 

(See drill exploration) 

Drop bottom. 179 

“ forging. 318 

“ tests. v .309-515 

Dry bases of analysis.. 41 

Dry blast. 150 

Dry chemistry.;. 15 

Drying Bessemer bottoms. 186 

“ blast furnace. 152 

“ O. H. furnace. 218 

Ductility. 5 


Duquesne Works. 368 

rail joint.!.453455 

gas cleaning plant. 147 

Duplex process.293 to 297 

“ slag. 297 

Dust catcher. 146 

Dynamic stress. 301 

Dynamo. 250 

Dyne. 243 

Eccentric converter. 180 

Edgar Thomson mills. 447 

splice bar shop. 458 

works. 180 

Edging pass.462468471 

Efflorescence. 15 

Effusion. 5 

Elastic deformation. 304 

“ limit.303-307 

Elasticity. 4 

Electric arc. 264 

“ furnaces. 265 

“ current.246 to 256 

“ furnace slag. 208 

“ furnaces.261 to 267 

“ heating.262 to 267 

“ pyrometers. 64-65 

“ steel, properties of.289 to 291 

“ steel, uses of. 291 

Electrical resistance pyrometer. 64 

Electrodes.277-279 

Electrolysis. 14-261 

Electrolytes. 8 

Electro magnetic induction.249-250 

Electromotive force. 246 

Electron (theory). 13 

Element, chemical. 9 

Elongation, per cent, of.301-307 

Empirical formula. 68-69 

Endothermic reaction. 8-16 

Energy. 5-243 

“ kinds of. 6 

“ laws of. 6 

Erg... 244 

Ethane. 70 

Ether. 7 

Ethylbenzene.105-106 

Ethylene. 69 

Eutectic alloy.348-523 

Eutectoid. 525 

“ steel.525-527 

Exothermic reaction. 8-16 

Expansion tests. 34 

Exploration for iron ore. 47 

Explosion doors. 141 

Extension. 4 


















































































































604 


WORD INDEX 


Faggots. 174 

Fahrenheit scale. 7 

Falling weight test (see drop test). 309 

Fatigue stress. 301 

Feldspar. 29-36 

Ferric oxide. 22-36 

Ferrite.... . 518 

“ in pig iron. 127-524 

“ “steel.518-524 

Ferro chromium. 228 

“ manganese.129-190-228 

“ phosphorus. 228 

“ silicon. 129-190-228 

* ‘ vanadium. 228 

Ferroso-ferric oxide. 22-36 

Ferrous and ferric compounds. 27 

“ compounds. 27 

“ oxide in open hearth. 234 

“ products. 169 

“ sulphate. 27 

Fibrous structure. 170 

Fillet. 408 

Fin.336-494 

Finish on bars.489-495 

Finished products.418-515 

Finisher (see finishing stand). 337 

Finishing period in O. H. process. 270 

“ rails.450-452 

c “ rolls. 337 

spli debars. 452 

stand. 337 

“ steel.190-226 

temperature.313-450 

Fire brick. 32 

“ clay. 32 

“ clay brick. 32 

“ cracks on rolls. 495 

“ damp. 69 

Firestone. 185 

First helper. 218 

Fish oil for hardening.•«. 552 

Fixed carbon. 76-85 

Fixed converter. 183 

Flame in converter. 188 

“ “ open hearth. 220 

Flare on hoop. 473 

Flats, finish of. 489 

“ rolling of. 468 

Floors in open hearth. 209 

Flue dust. 38-146 

Fluid compression. 2 

Fire clay... 29 

Fluor spar.120-223-268-270 

Fluorine. 12 


Flushing cinder (see tapping slag) 

tar.. 

Flux. 

“ in the electric furnaces. 

Flying shear.. 

Foot-pound. 

Force. 

Forge iron. 

Forging. 

“ axles. 

“ hammer. 

“ press — ‘. 

“ tests. 

“ wheel blanks. 

Former bar. 

Foundry iron.. 

Four pass stove. 

Fracture tests at blast furnace... 

“ “ “ open hearth_ 

Fractures of steel. 

Free cementite.. 

“ ferrite. 

Freezing of alloys.. 

Frick Coke Company. 

“ Furnace... 

Frothing slag (see run off). 

Fuels. 

“ for open hearth. 

Fuel oil. 

Full annealing. 

Fume from converter. 

Furnace cooling. 

“ lines. 

Fusion tests. 



122 

... 98-99 
117 
271 
404 
244 
243 

129 j 
...316-318 I 
. . .508-510 

316 

317 I 

495 ] 

499 , 

512 

129 

142 

155 

224 

. . .305-537 
.. .520-526 
...520-526 
521 to 526 
86 
264 
222 
58 to 116 
203 
69 
540 
193 

...459-545 

137 

33 


Gag. 451 

Gag press. 451 

Gallium. 11 

Gamma iron. 532 

Gangue. 39 

Ganister. 29 

“ brick. 29-32 

Gas. 2 

“ holes (see blow holes). 346 

“ port.'.. 211 

“ producer. 71 to 75 

“ volume, law’s of. 2 

“ washer.*.. 148 

Gaseous fuels.. 70 to 75 

Gasoline. 69 

Gayley dry blast..,. 150 

Generalized formula. 68-69 

Generator, electric. 250 

Girod furnace. 266 

Glucinum. 11 































































































































WORD INDEX 


605 


Gob. 86 

Goethite. 37 

Gogebic iron range. 43 

Gold." 11 

Gold-silver alloys. 521 

Goose-neck. I 35 

Gothic pass. 323 

Grading ores... 55 

Grains.533-538 

Gram. 4 

calorie (see small calorie). 7 

molecular volume. 13-21 

weight. 21-61 

Granulated slag. 152 

Granulating pit. 152 

Granulation of steel... 534 

Graphite.23-31-32 

Graphitic carbon. 127 

Gravitation, law of. 4 

Gray iron. 127 

Greene furnace. 264 

Grizzleybar. 98 

Gronwall furnace. 266 

Grooved roll. 323 

Grooves in rolls. 323 

Guard. 334 

Guide.334-475 

“ rounds. 467 

“ marks. 415 

“ mill.330-475 

Gun brick.*.. 94 

“ for blast furnace. 155 

Half cup fracture. 306 

Hammer forging. 316 

“ steam. 316 

Hammering, principles of. 317 

Hand guide mill. 475 

“ mill.330-474 

“ round. 467 

Harden furnace. 264 

Hardening carbon. 533 

process of. 548 

Hardness. 5 

“ number. 311 

“ test. 309 

Head, of rails. 440 

“ “water. 245 

Hearth brick. 137 

“ jacket. 132 

“ of blast furnace. 132 

“ of open hearth. 210 

“ ’and bosh brick.137-138 

Heat. 6 

“ cracks in rolls. 495 

“ of formation... r . 60 

Heat of fusion. 59 


Heat of vaporization. 

“ reactions in blast furnace... 

“ converter. 

“ treating, axles.. 

car wheels. 

“ rail joints . 

treatment. 

“ units. 

Heater.. 

Heating furnace. 

cinder. 

Heavy naphtha. 

“ rails. 

Helix. 

Helical Pinions. 

Hematite. 

Heptane. 

Heroult furnace. 

Hexagon, rolling of. 

Hexane.. 

High carbon steel. 

Hiorth furnace. 

Hoist for blast furnace. 

Holley, Alexander. 

Hollow boring for axles. 

Homogeneous substance. 

Hooke’s law. 

Hoop. 

“ finishing of.. 

“ mills.. 

“ rolling of. 

Hopper of blast furnace. 

Horse power. 

Hot blast. 

“ “ main. 

“ “valve.... 

Hot iron. 

“ metal. 

“ rolling. 

“ sawing. 

“ short.. 

“ spots. 

“ templet_.-.*.. 

“ top mould. 

“ worked splice bars. 

“ working. 

Housings. 

“ screw. 

“ top. 

Howard Axle Works. 

Hughes gas producer. 

Huntch pit (see slag pit). 

Hydraulic press (see forging press) 

pressure. 

units. 

Hydrocarbon. 


. 59 

.163-164 

. 194 

.513-515 

. 506 

.459 to 461 

.539 to 568 

. 7 

.336-362 

.419 to 422 

.419-421 

. 102 

. 448 

. 247 

. 334 

. 36 

. 70 

.266-275 

. 469 

. 70 

. 226 

. 264 

. 140 

. 177 

. 513 

. 8 

. 4 

. 470 

. 473 

. 470 

.470 to 473 

. 139 

. 244 

. 150 

. 135 

. 143 

.127-171 

. 221 

. 313 

....450-466-468 

. 176 

. 158 

441 

. 346 

. 460 

.313 to 321 

322-332-368-378 

.333-370 

.......333-370 

.508 to 515 

. 73 

. 222 

. 318 

. 245 

. 245 

. 24 




























































































































606 


WORD INDEX 


4 

Hydrochloric acid. 21 

Hydrogen. 12-22 

Hydroquinol. 109 

Hydroxide. 19 

Hygroscopic. 16 

Hyper-eutectoid steel. 526 

Hypochlorous acid. 18 

Hypo-eutectoid steel. 526 

Hysteresis. 530 

Idiomorphic crystals. 533 

Ignition point (see kindling temperature). 70 

Impact stress. 301 

“ test. 34-309 

Impedance. 259 

Impenetrability. 4 

Impurities in steel. 518 

Incipient crack. 508 

Indigo. 113 

Inductance. 259 

Induction furnace. 263 

Inertia.. 3 

Ingot. 342 

Ingot defects.342 to 351 

“ mould.182-205 

Ingotism. 348 

Inorganic chemistry. 8 to 27 

Inspection.417-430-451-493-498-504-509 

department. 493 

of merchant mill products . . 493 to 495 

“ plates. 430 

“ “ rails. 451 

“ semi-finished products. 417 

“ wheels. 504 

Insulator.. 245 

Invar. 582 

Inwall.136-137 

“ brick.;.137-138 

Iodine. 12 

Ions. 14 

Iron.12-27-125 

“ action in the converter. 194 

“ carbonate.27-36-37 

“ early history of. 125 

“ notch. 132 

“ ore. 36 

“ oxides. 36 

“ oxides in open hearth. 232 

“ pyrites. 36 

“ silicates. 36 

“ sulphates. 27 

“ sulphides. 36-39 

Irregular fracture. 306 

Isomeric compounds. 105 

Jacket. 132 

Jones, W. R. 177 


Joule.244-245 

Journal. 512 

Jump roll: a plain roll with collars on each 

end. Used in rolling flats. _ 


Kaolin (see clay). 29 

Keeper, one in charge of a blast furnace. 

Keller furnace. 266 

Kelly, Wm. 176 

Kerosene. 69 

Kidney ore. 37 

Kilogram. 4 

meter. 244 

Kilometer. 4 

Kilowatt.. 244 

“ hour.244-262 

Kindling temperature of gases. 70 

Kinks. 494 

Kish, graphite-like substance given off by 

pig iron. 

Kjellin furnace. 263 

Koppers by-product coke oven. 93 

Laboratory tests on fuels. 62 

“ “ refractories. 33 

Ladle, steel. 204 

“ additions.190-226 

“ reactions. 191 

“ test (see sampling).192-229 

Lag (see hysteresis). 530 

Lake Superior ore. 79 

“ “ “district. 42 

Lamination. 435 

Lap.336-494 

Lard oil in quenching. 552 

Large calorie. 7 

Larry. 86-97 

Latent heat. 59 

Lauth, B. C. 423 

“ mill. 423 

Law of constancy of nature. 15 

“ “ definite proportions. 9 

“ “ ebulition. 59 

“ evaporation. 59 

“ “ fusion. 59 

“ heat exchange. 58 

“mass action. 4 

“ multiple proportions. 10 

Lead. n 

bath, quenching. 552 

hardening (see quenching in lead).... 552 

“ tempering...''.... 557 

Lead-tin alloy. 523 

Leading spindle. 333 

Leg pipe. 135 

Lenz’s law. 250 

Leveling in coke oven. 88 

























































































































WORD INDEX 


607 


Liberty mill. 425 

Lifting table.335-380 

Light oil.101-102-115 

“ rails. 452 

Lignite. 66-77 

Lime. 30-39 

“ boil.r. 223 

“ cooling. 545 

Limestone. 25 

analysis of.120-160 

as a flux. 119 

in blast furnace.160-170 

“ in open hearth.223-239 

Limiting angle of rolling. 340 

Limnite. 37 

Limonite. 36-37 

Liner. 332 

Lining of blast furnace. 137 

“ converter. 184 

“ “ electric furnace. 275 

Linseed oil, quenching. 551 

Liquid. 2 

Lithium. 11 

Locus of a point. 521 

Lodestone (see magnetite). 36 

Longitudinal ovens. 90 

“ test piece. 434 

Looping mill. 330-477 

Lorry (see larry). 97 

Loss in head. 245 

Low carbon steel. 226 

Lower Freeport coal bed. 79 

“ Kittanning coal bed. 79 

Lug. 182 

Lump ore. 38 

Lute. 97 


Machine cast pig. 152 

Macroscopic structure. 518 

Macro-structure. 518 

Magascopic (see macroscopic). 518 

M agnesia.25-30-39-166 

Magnesian limestone (see dolomite) 26-31-119-231 

Magnesite.25-32-228-231 

Magnesium. 11-25 

Magnet. 247 

Magnetic fields. 247 

flux. 247 

“ induction. 248 

iron ore (see magnetite).27-36-37 

permeability. 248 

“ substance. 247 

Magnetism. 246 

Magnetite.-. 27-36 

Making bottom...... 218 

Malleable castings. 172 

“ cast iron. 172 


Malleability. 5 

Manganese.11-27-128-176-235 

in converter. 194 

“ in steel. 570 

sulphide. 286 

in steel for case hardening. 563 

Manipulator. 373 

Mantle of blast furnace. 136 

Marquette ore range. 43 

Marsh gas. 69 

Martensite. 526-549-550-553-558 

. 584 

. 201 

. 201 

. 4 

. 17 

. 544 

. 585 

. 2 

. 2 

. 2 

. 3 

. 2 

. 551 

. 304 

. 304 

. 591 

. 8 


Martensitic nickel steel. 

Martin Brothers. 

“ process. 

Mass. 

“ action, law of. 

Massive pearlite. 

Matrix. 

Matter. 

“ classes of. 

“ conservation of. 

“ sciences of. 

“ states of. 

Matthews and Stagg. 

Maximum load. 

“ stress. 

Mayari steel. 

Mechanical mixture. 

properties.299-301-303-304 

Medium carbon steel. 226 

Melter. 218 

Menominee ore range. 43 

Merchant bar. 173 

“ mill.474-482 

Mercury. 11 

“ as quenching agent. 551 

Metadihydroxylbenzene. HO 

Metal. 9 

Metalloid. 9 

Metallurgy. 2 

Metasilicic acid. 123 

Metaxylene.105-106 

Metcalf’s Experiment. 537 

Meter. 4 

Methane. 69-70 

Metric system. 4 

Micro structure. 518 

Microscopic structure. 518 

Middle Kittanning. 79 

Mil. 256 

“foot . 257 

Mill, classes of. 365 

“ shoe.322-332 

Milling pit.— • 52 

“ system of mining ore. 50-52 

Mineral. 36 

“ oil in quenching. 551 

























































































































608 


WORD INDEX 


Missabe ore range. 46 

Mixer. 181-204 

Modolus of elasticity.301-307 

Molds for ingots.182-205 

Molecule. 2 

of elements. 13 

Molecular weight. 19 

Molten metal (see hot metal). 221 

Molybdenum. 11 

M onell charge. 219 

“ process. 201 

Monkey for blast furnace. 134 

“ cooler. 134 

Morgan, C. H. 397 

“ mill. 397 

Mothballs. 113 

Motor Benzol.•.'. 107 

Mother liquor.100-521 

“ metal. 525 

Moulds for ingots.182-205 

Muck bar. 173 

Multiple proportions. 9 

Muriatic acid (see hydrochloric acid). 21 

Mushet, R. 176 

Naphtha.69-101-105-111 

Naphthalene.101-113-114 

Naphthionic acid. 114 

Naphthol. 114 

Nascent state. 13 

Natural gas. 66-71 

Neck of a roll. 322 

Necking of test piece. 305 

Neutral flux. 120 

“ refractories. 31 

“ substance (see salt). 8 

Nickel. 11-228 

“ steel. 580 

“ in steel for case hardening. 563 

Nickel-Chrome steel. 590 

Nigger heads in open hearth. 224 

Ninety per cent, benzol.103-107 

Nitric acid. 25 

Nitrobenzene. 109 

Nitrogen. 12-25 

“ in blast furnace. 165 

Nitronaphthalene. 114 

Nitrotoluene. 112 

Nodulizing (see spheroidizing). 547 

Nomenclature. 18 

Non Bessemer ore. 40 

“ coking coal. 80 

“ electrolyte. 8-9 

“ metal. 9 

Normalize. . 547 

Nose of converter. 183 


Occlusion see absorption). 5 

Octane. 70 

Off takes. 140 

Ohm. 245-257-262 

Ohm’s law. 256 

Oil and tar burner. 68 

“ hardened (see oil quenched). 551-552-553 

“ scrubbers. 101 

“ temper (see also oil quenched).551-558 

“ of vitrol (see H2SO4). 23 

One level type of open hearth. 209 

Open hearth. 209 

“ process. 198-242 

“ “ slag.122-234-242 

“ steel, making of. 198-242 

“ pass. 323 

“ pit. 48-50 

“ “ mining. 50 

“ top blast furnace. 139 

Optical pyrometer. 65 

Ore. 36 

“ analysis of. 160 

“ boil. 222 

“ bridge. 151 

“ composition of. 36-37 

“ down. 224 

“ grading of. 55 

“ transportation of. 56 

“ valuation of. 38 

Orientation. 533 

Orthosilicic acid. 123 

Ortho xylene.105-106 

Oval groove. 467 

Overblown steel. 575 

Overburden. 53 

Oxidation. 16 

Oxide. 16 

Oxygen. 12-22 

“ in blast furnace. 162 

in the electric furnace.268-269 

in steel. 575 

Palaeozoic era. 79 

P and A tar extractor. 99 

Parabenzene sulphonic acid. 110 

Paraffin wax. 69 

Paraxylene.105-106 

Pass in rolling.323-337 

Pass-over mill (see pull-over mill).. 330 

Pass templet. 441 

Pearlite.!.127-520-525 

“ in pig iron. 127-524 

“ in steel.519-523-526 

Pearlitic chrome steel. 588 

nickel steel. 584 

Peat. 66-77 

























































































































WORD INDEX 


609 


Pen stock. 

Pentane. 

Permanent magnet. 

set. 


. 135 

. 70 

. 247 

. 303 

Petroleum.. 66-68 


Phase of electric current. 

. 253 

“ “ pearlite. 

. 543 

Phenylhydracine. 

.. “. 108 

Phenol.. 

. 110 

Phosphoric acid. 

25 

Phosphoretic steel. 

. 574 

Phosohorus. 

. 12-25 

in blast furnace.... 

. 165 

electric furnace.. 

. 268 

“ open hearth. 

. 237 

“ ore. 

. 40 

“ pig iron. 

. 129 

“ “ steel. 

. 573 

Phthalic acid. 

. 114 

Phthalimide. 

. 113 

Physical change. 

. 8 

“ properties. 

. c ... 3 

“ of plates. .. 

. 433 

“ testing of steel. 

. 300 

Picric acid. 

. 110 

Pickling test. 

. 495 

Pig and ore process. 

. 199 

“ “ scrap process. 

. 201 

“ casting machine. 

. 152 


“ iron, composition of.127-174-228 

“ nickel. 228 

Pigging up. 224 

Piling, rolling of. 465 

Pillaring. 158 

Pinions.322-333-369-378 

“ housings. 333 

Pipe.343 to 346-495 

“ in axles.508-512 

Pit annealing. 545 

“ casting. 324 

Pitch for rolls. 382 

“ line. 328 

Pittsburgh coal bed. 79 

Plain steel. 579 

Planishing pass. 337 

rolls. 337 

Plastic clay. 29 

“ deformation.. 305 

Plasticity. 5 

Plate mills. 423-435 

Plates, kinds of. 423 

“ rolling of.423-425-428 

Platinite. 582 

Platinum. 11 

Pneumatic process. 175 

Poling. 192 

Polyphase currents, electric. 253 


Pony roughing stand. 

Porosity. 

Potash (K2O). 

Potassium. 

Potential. 

Pouring (see teeming) 

Powdered coal. 

Power... 

“ factor. 

Preliminary test. 

Press, forging. 

Pressing (see forging). 
Pressure on gases.... 
Primary austenite 
Prismatic sulphur.... 
Producer. 


Progressive distillation analysis ... 

hardening. 

Propane. 

Properties of matter. 

Prospecting for ore. 

Proximate analysis. 

Puddle bar (see muck bar). 

“ iron (see wrought iron) 

Pulling test. 

Pull-over mill. 

Pulpit. 

Pulverized coal (see powdered coal) 

“ burner. 

Punching splice bars. 

Purification processes. 

Pyro-chemical process. 

Pyrometers. 


337 

4 

20 

. 12-166 

243 
.192-228 

81 

244 
259 
287 
317 
317 

2 

525 

23 

71 

. 66-71 
. 75-76 
553 
70 
3 

47 

. 75-76 
173 
173 
301 
330 
179 
81-82-83 
84 
459 
175 
126 
64 


Quartz. 24-36 

Quartzite (see quartz). 

Quenching.548-551 

bath.. 552 

media. 552 

“ tank. 514 

Quicklime (see calcium oxide). 25 

Quick silver (see mercury). 11 

Rabble. 230 

Radiation. 59 

“ pyrometer. 65 

Radical. 14 

Ragging. 340 

“ marks. 415 

Rail, evolution of. 437 

“ joints, rolling of. 454 

“ “ treatment of . 459 

“ “ types of.453-454 

“ mills...442 to 449 

“ rolling of.448 to 452 

“ steel, Bessemer. 190 



























































































































610 


WORD INDEX 


Raises. 53 

Raw materials (see basic materials). 58 

Reactions, chemical. 13 

in blast furnace.163-171 

Reaumur. 7 

Recalescence. 527 

Recarbonizing (see recarburizing).191-226 

Recarburizing, Bessemer steel.. 191 

“ open hearth steel. 226 

Recuperative furnace.421-422 

principle.. 63 

Red ore. 36 

“ short (see hot short). 176 

Redstone coal bed. 79 

Reduction. 16 

“ of area.301-307 

Refractories. 28 

Regenerative chambers.212-217 

furnace. 419 

principle. 63 

Reheating furnace.419 to 422 

Repeater.330-479 

Repeating mill. 330 

Rephosphorization.226-298 

Rerun benzol.103-104 

“ toluol. 104 

Resorcinol. 110 

Residual manganese. 191 

Resiliency. 575 

Resistance, electrical. 256 

furnace. 263 

pyrometer. 64 

Resting period. 302 

Retardation. 527 

Retention theory. 555 

Retort coke (see by-product coke).85 to 98 

“ oven (see by-product coke). 93 

Reverberatory furnace. 420 

Reversing mill.330-366-367-368-369 

Rhombic sulphur. 23 

Roasting (see calcining). 25 

Roll bearings.331-371 

“ design for billet mills.394-402 

“ “ “ blooming mills 373-377-379-383 

“ “ merchant mills. 482 

“ “ “ rails. 438-447 

“ general remarks. 327 

“ how to study. 438 

“ marks.. 495 

“ size of.327-384 

“ table. 335 

“ tables. 322 

Rolling defects.413-494 

“ history of. 318 

principles of.319-321 


Rolls. 

“ for billet mills. 

“ “ blooming mills. 

Roof of open hearth. 

Rotary shears. 

Rough surface, cause of 

“ turning axles. 

Roughing passes. 

stand. 

“ rolls. 

Rounds, kinds. 

rolling of. 

“ straightening of 

Run off slag. 

Run-of-mine coal. 

Runners. 

Running stopper. 


.322 to 331 

... .393-400-402 
371-377-379-383 

. 211 

. 429 

. 415 

. 512 

444-450-483484 

477 

337-423-444446 

. 467 

. 467 

. 468 

. 222 

. 86 

.141-155 

. 205 


Saccharin. 112 

Sack’s mill. 331 

Salamander. 132 

Salt.?. 8 

Salt and ice. 522 

Salicylic acid. 115 

Sampling pig iron ... . 155 

“ steel. 192-229 

Sand. 32 

“ as a flux. 118 

“ as a refractory. 29 

“ bottom furnace. 419 

“ roll. 323 

“ seal. 514 

“ test. 155 

Sandstone (a sedimentary rock). 

Saturated solution. 522 

Sauveur. 517 

Scabs.349-415 

Scaffolding. 158 

Scale. 233 

Scarf. 538 

Schedule for merchant mills.482-485 

Schoen, Chas. E. 497 

“ mill.331-500 

Scleroscope.•. 309 

Scramming. 50-53 

Scrap and pig process.201-219 

in Bessemer process. 188 

in open hearth process.201-219 

Screw down. 333 

“ steel. 190 

“ stock.190-572 

Scull (see skull).. .*. 225 

Seams, cause of.346-415 

“ in bars. 494 

in blooms, billets, etc. 415 

“ in rails. 452 

Second helper. 218 

































































































































WORD INDEX 


611 


Second strand.337-485 

Section mill (see shape mill). 461 

Seger cone. N _ 33 

Segregated cementite. 544 

Segregation. 348 

in axles.508-512 

Selective freezing. 524 

Selenium. 12 

Self-fluxing ore. 117 

“ inductance. 259 

Semi-continuous mill. 477 

finished products.364 to 414 

Sensible heat. 58 

Sesquioxide base. 124 

Seventy-two hour coke. 87 

Sewickley coal bed. 79 

Shaft of blast furnace (see stack). 136 

Shakedown. 225 

Shape mill. 461 

Shaped bloom. 463 

Shear foreman. 490 

“ steel. 174 

Sheared plate mill. 423 

Shearing defects. 415 

“ forces. 301 

“ plates.429-433 

“ slabs. 389 

“ stress. 301 

Shears for blooming mill. 372 

Sheet bar.190-408 

“ “ m iU.408-413 

“ “rolling of.406 to 413 

Shoe of a mill.322-332 

Shore scleroscope. 309 

Shrinkage of steel in ingot. 343 

Side blown converter. 183 

Side shears. 429 

Siderite. 37 

Siemens, William. 198 

Siemen’s direct process. 199 

“ furnace. 199 

“ pig and ore process. 201 

“ pyrometer (see water pyrometer) 64 

“ steel (see open hearth steel). 198 

Siemens-Martin process. 201 

Silica. 24-39 

“ brick. 29 

“ in Bessemer process. 194 

“ “ blastfurnace. 195 

“ “ open hearth process. 234 

“ “ ores. 39 

“ “ sand. 32 

Silicates.121-123 

Silicon, acids of. 

“ in converter. 194 

“ “ open hearth process. 

“ “ pig iron. 24-127-129-171 


Silicon in steel for case hardening. 563 

Silico-spiegel. 129 

Silver. 12 

Simple steel. 579 

Sine curve. 252 

Single coil of hoop. 473 

level open hearth (see one-level)... 209 

“ phase current. 252-3 

Sinkhead.206-324 

Sintering. 219 

Skelp. 190 

Skew back. 211 

“ brick. 211 

“ channels. 211 

Skewed rolls. 404 

Skimmer. 279 

Skin of ingot. 343 

Skip hoist. 140 

Skull. 225 

Slab. 365 

“ rolling of.385 to 390 

Slab-and-edging method of rolling flats... 468 

“ “ “ “ rails 438 to 449 

Slabbing mill.385 to 388 

Slaked or Slacked lime (CaO-j-EfeO). 


Slag. 

... .15-120-152 

“ in Bessemer process. 

. 122 

“ “ blast furnace. 

. 121 

“ “ electric process. 

.122-288 

“ functions of. 

. 120 

“ hole. 

. 210 

“ notch (see cinder notch)...... 

. 134 

“ in open hearth process. 

...122-234-242 

“ pockets. 

. 211 

Slagging tests. 

. 34 

Sleeve brick. 

. 205 

Slicing, system of mining. 

. 53 

Slips. 

. 157 

Slivers. 

.415-494 

Sloppy heat. 

. 128 

Slurry. . 

. 138 

Small calorie. 

. 7 

Smelt... 

. 117 

Snake.. 

. 435 

Snort valve. 

. 150 

Soaking ingots. 

.359-362 

“ pit. 

.342-352 

“ “ efficiency of. 

. 362 

Soda (same as sodium oxide). 


(also sodium carbonate). 



. 11-160 

Soft steel (see low carbon steel)... 

. 226 


. 2 

“ solution. 

.519-521 




















































































































612 


WORD INDEX 


Solute, dissolving substance. 

Solution. 8 

Solvent, substance dissolved. 

“ naphtha. 113 

Sorbite.543-559 

Sorbitic steel. 543 

Spalling test. 35 

Spanner bar. 432 

“ block.!. 432 

Spar (see fluor spar). 120 

Spawling tests (see spalling tests). 35 

Special steel. 579 

Specific gravity. 5 

“ heat. 58 

“ “ pyrometer. .. ,. 64 

“ resistance. 257 

Speed in rolling. 339 

Spheroidize. 547 

Spiegel.129-190-228 


“ cupolas.180-204 

Spindle.322-334-369-378 

Splasher. 132 

Splice bar.453-461 

“ “analysis of. 190 

“ “ finishing of. 458 

“ “rolling of. 454 

Spoon. 225 

Spout of open hearth. 210 

Spread in rolling.319-328 

Spring heat (spring steel heat). 

Square mil. 257 

Stack of blast furnace. 136 

“ “ open hearth furnace. 217 

Stand of rolls. 322 

Standard ferro. 129 

Standards (see housings). 322 

Star connections. 255 

Stassano furnace. 265 

Static stress. 301 

Stationary furnace (one not movable). 

Stead. 533 

Steam shovel mining. 48-50 

Steel. 173 


“ ladle. 204 

“ rolls.323-326 

“ spout. 210 

“ tie, rolling of. 465 

Sticker. 224 

Stock distributor. 140 

“ house. 151 

“ indicator. 140 

“ line. 133 

“ pile (see ore pile).131-150-151 

“ yard.131-207 

Stone (see limestone). 25 

Stool. 182 


Stopper.182-205 

Stove burners. 143 

“ linings. 145 

“ valves. 143 

Stoves, kinds of. 142 

Straightening axles. 511 

bars. 492 

machine.427-468-492 

plates.427-433 

press.451-511 

rails. 451 

rolls. 427 

rounds. 468 

shapes. 466 

Strain. 5 

Strand. 337 

Stratified structure. 519 

Straw oil. 101 

Stress. 5 

“ kinds of. 301 

Stretch (see elongation).301-307 

Strip. 470 

Stripper.181-205 

Stripping.... 50-51 

Structural formula. 68-69 

shapes, rolling of.461 to 469 

“ steel, testing of. 301 

Subcutaneous blow holes (see blow holes 

near the skin). 346 

Substance. 2 

Sulphanilic acid. 112 

Sulphates (see salts of sulphuric acid).... 27-116 

Sulphides. 18 

Sulphur. 12-23 

in Bessemer process. 175 

“ blastfurnace.165-171 

“open hearth. 236 

“ore . 39 

“ pig iron. 128 

Sulphuric acid. 23 

Sulphurous acid. 19 

Superficial hardening. 568 

Surface defects. .■.413-435-451-494-504 


Surface hardening (see case hardening)., 

Sweat. 

Swedish Bessemer process. 

“ iron. 

Sweep. 

Symbols, chemical.... 

Synthesis. 


562 

221 

176 

176 

324 

9 

16 


Table, of a tee shape 

Tables, of a mill_ 

Talbot furnace. 


. 466 

. 335 

.. 294 

“ process. 201 

Tandem mill (see Belgian mill). 477 






























































































































WORD INDEX 


613 


Tap a heat (see tapping furnace).154-225 

Tap hole, blast furnace. 132 

“ open hearth furnace. 210 

Tape size. 504 

Tapping, blast furnace. 154 

electric furnace. 281 

hole.132-210 

open hearth furnace. 225 

rod. 225 

slag (see basic slag). 122 

Tar. 99-114 

“ as a fuel. 67 

“ burner.. 68 

“ extractor. 99 

“ refinement of. * 114 

“ uses of. 115 

Teaming (same as teeming). 192-228 

Tee rail. 436 

“ rolling of. 466 

Teeming, Bessemer steel. 192 

electric steel. 281 

“ ladle.182 

open hearth steel. 228 

Temper colors. 556 

Temperature. 6 

tests in open hearth. 225 

Tempering. 554 

austenic steel. 558 

martensitic steel. 558 

troostitic steel. 558 

Templet.439-440-441-442 

Temporary magnet. 248 

Tenacity (see tensile strength). 301 

Tensile strength.301-307 

Tensional stresses. 301 

Terminology. 18-19 

Ternary compounds. 18 

“ steels.580-584-587-595 

Test Mould. >5. 229 

Test piece.302-309 

“ spoon.224-225 

Testing axles. 515 

“ machine..303-309 

“ refractories. 33 

“ steel.299 to 311 

Theisen’s cleaner. 149 

Thermal capacity. 58 

critical points.527 to 533 

Thermo- electric couple. 64 

“ pyrometer. 64 

Thermometer. 6-7 

Thomas-Gilchrist process.175-177 

Three-high blooming mill.377 to 384 

“ “ mill. 330 

“ pass stove. 142 

“ phase current.253-255 

Ties, rolling of. 464 


Tilt hammer. 316 

Tilting converter. 183 

“ furnace.200-294 

“ table. 335 

Tin. 11 

“in steel. 577 

Titania (TiC>2). 166 

Titanium. 12-165 

T. N. T. Ill 


Tolerance, reasons forl90-226-329-348-428-430-467 

Toluene. Ill 

“ sulphonic acid. 112 

Toluidin.. 112 

Toluol.101-105-106-111-112-113 

Tongue and groove pass. 406 

Top brick.137-138 

“ of blast furnace.139-141 

Torsional stresses. 301 

“ test. 308 

Total car bon. 127 

Toughening. 559 

Trade heat. 219 

Train of rolls. 477 

Transformation range (see critical range) 527 

Transformer. 260 

Transporting ores. 56 

Tri-basic acid. 19 

Trinitrotoluol (T. N. T.). Ill 

Triplex process. 297 

Troostite.550-556 

True annealing. 540 

Trunnel head. 87 

Try hole. 140 

Tub (see ladle). 204 

Tungsten. 12 

Turgite. 37 

Turning rolls. 329 

Tuyere. 134 

“ brick. 134 

“ cooler. 134 

“ cap. 135 

“ stock. 135 

Tweer (see Tuyere). 134 

Twere (see tuyere). 134 

Twisted guide (see twisting guide). 400 

Two Level Open Hearth. 209 

Two-high mill. 330 

Two-pass stove. 142 

Two phase current. 253 

Twyere (see tuyere). 134 


Ultimate analysis. 75-76 

strength. 304-307 

Uncombined carbon (see graphite). 127 

Underfill. 494 


















































































































614 


WORD INDEX 


Universal mill.330-431-433 

“ plates. 432 

Up-and-down takes. 211 

Upper Freeport coal bed. 79 

“ Kittanning coal bed. 79 

Upset test. 495 

Uranium. 11 

Valence. 10 

Vanadium. 12 

in case hardening. 563 

steel. 595 

Vaporization, heat of. 59 

“ “in hardening. 552 

V-connection. 225 

Vermilion ore range. 46 

Vibrating spindle..334-370 

Viscosity of quenching liquid. 552 

Volatile matter of coal. 76-98 

Volt. 245-262 

Voltaic cell. 246 

Wabbler (see wobbler). 322 

Wall of blast furnace. 136 

Walls of open hearth. 210 

Wash heat. 219 

“ oil. 101 

Washing open hearth furnace. 219 

Waste heat. 87 

Water, composition and formula. 13 

* ‘ annealing. 545 

“ pyrometer. 64 

“ cooling. 551 

“ gas. 71 

“ hardening (see quenching). 551 

“ quenching. 551 

“ seal. 73 

“ separator. 149 

“ trough. 139 


Watering coke. 89-97 

Watt. .4 245-262 

Watt-hour. 262 

Waynesburg coal bed.. 79 

Web holes. 504 

“ of a rail.440-442-449 

Welding steel. 538 

Well of open hearth. 212 

W ellman f urnace. 200 

Wenstrom mill. 331 

Wet chemistry. 15 

Wheel blank.497-504 

“ seat.•. 512 

White annealing. 540 

“ • metal. 331 

Wicket. 211 

Wind box. 186 

Window of housings. 332 

Wobbler. 322 

Wood. 66-76 

Work. 243 

“ effects of on steel.312-535 

Working period in open hearth. 223 

Works annealing. 540 

Wrought iron.170-171-173 

Xanthosiderite. 37 

Xylene. 105 

Xylol. 105 

Yield point... 303 

Y connections. 255 

Yellow brass. 331 

Youngs modulus. 307 

N 

Zee’s (or Z’s). 466 

Zinc. 11 

“ in blast furnace. 166 

Zone of fusion.167-169 


381 92 




















































































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